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	$231.91	8.451%	$251.5087	$251.51	$251.50	$251.50
Purchase #2	$113.35	12.817%	$127.8781	$127.88	$127.90	$127.90
Purchase #3	$208.40	8.365%	$225.8327	$225.83	$225.85	$225.80
Purchase #4	$139.68	9.213%	$152.5487	$152.55	$152.55	$152.50
Purchase #5	$160.29	3.807%	$166.3922	$166.39	$166.40	$166.40
Purchase #6	$10.58	4.414%	$11.047	$11.05	$11.05	$11.00
Purchase #7	$207.27	6.514%	$220.7716	$220.77	$220.75	$220.80
7 purchase totals =	$1,071.48		$1,155.9790	$1,155.98	$1,156.00	$1,155.90