Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$105.78	8.686%	$114.9681	$114.97	$114.95	$115.00
Purchase #2	$138.86	8.131%	$150.1507	$150.15	$150.15	$150.20
Purchase #3	$247.93	13.703%	$281.9038	$281.90	$281.90	$281.90
Purchase #4	$81.27	8.738%	$88.3714	$88.37	$88.35	$88.40
Purchase #5	$155.46	4.282%	$162.1168	$162.12	$162.10	$162.10
Purchase #6	$200.92	5.194%	$211.3558	$211.36	$211.35	$211.40
Purchase #7	$200.89	8.745%	$218.4578	$218.46	$218.45	$218.50
7 purchase totals =	$1,131.11		$1,227.3244	$1,227.33	$1,227.25	$1,227.50