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	$60.91	9.528%	$66.7135	$66.71	$66.70	$66.70
Purchase #2	$163.29	9.131%	$178.2	$178.20	$178.20	$178.20
Purchase #3	$85.72	6.423%	$91.2258	$91.23	$91.25	$91.20
Purchase #4	$217.33	8.540%	$235.89	$235.89	$235.90	$235.90
Purchase #5	$140.84	10.154%	$155.1409	$155.14	$155.15	$155.10
Purchase #6	$152.58	8.500%	$165.5493	$165.55	$165.55	$165.50
Purchase #7	$182.43	9.424%	$199.6222	$199.62	$199.60	$199.60
7 purchase totals =	$1,003.10		$1,092.3417	$1,092.34	$1,092.35	$1,092.20