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	$90.94	13.649%	$103.3524	$103.35	$103.35	$103.40
Purchase #2	$215.38	3.243%	$222.3648	$222.36	$222.35	$222.40
Purchase #3	$159.54	7.630%	$171.7129	$171.71	$171.70	$171.70
Purchase #4	$85.51	13.313%	$96.8939	$96.89	$96.90	$96.90
Purchase #5	$75.42	9.199%	$82.3579	$82.36	$82.35	$82.40
Purchase #6	$212.52	6.767%	$226.9012	$226.90	$226.90	$226.90
Purchase #7	$127.44	11.653%	$142.2906	$142.29	$142.30	$142.30
7 purchase totals =	$966.75		$1,045.8737	$1,045.86	$1,045.85	$1,046.00