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	$231.29	9.557%	$253.3944	$253.39	$253.40	$253.40
Purchase #2	$88.29	13.712%	$100.3963	$100.40	$100.40	$100.40
Purchase #3	$89.81	11.680%	$100.2998	$100.30	$100.30	$100.30
Purchase #4	$174.69	3.131%	$180.1595	$180.16	$180.15	$180.20
Purchase #5	$146.91	13.136%	$166.2081	$166.21	$166.20	$166.20
Purchase #6	$233.86	4.616%	$244.655	$244.66	$244.65	$244.70
Purchase #7	$156.73	5.290%	$165.021	$165.02	$165.00	$165.00
7 purchase totals =	$1,121.58		$1,210.1341	$1,210.14	$1,210.10	$1,210.20