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	$38.52	3.481%	$39.8609	$39.86	$39.85	$39.90
Purchase #2	$193.38	10.831%	$214.325	$214.33	$214.35	$214.30
Purchase #3	$55.92	5.753%	$59.1371	$59.14	$59.15	$59.10
Purchase #4	$213.44	5.472%	$225.1194	$225.12	$225.10	$225.10
Purchase #5	$66.31	5.144%	$69.721	$69.72	$69.70	$69.70
Purchase #6	$92.57	7.664%	$99.6646	$99.66	$99.65	$99.70
Purchase #7	$165.89	13.675%	$188.5755	$188.58	$188.60	$188.60
7 purchase totals =	$826.03		$896.4035	$896.41	$896.40	$896.40