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	$210.74	6.444%	$224.3201	$224.32	$224.30	$224.30
Purchase #2	$85.51	4.268%	$89.1596	$89.16	$89.15	$89.20
Purchase #3	$246.61	4.121%	$256.7728	$256.77	$256.75	$256.80
Purchase #4	$35.52	10.426%	$39.2233	$39.22	$39.20	$39.20
Purchase #5	$99.89	8.590%	$108.4706	$108.47	$108.45	$108.50
Purchase #6	$105.88	4.802%	$110.9644	$110.96	$110.95	$111.00
Purchase #7	$130.33	7.829%	$140.5335	$140.53	$140.55	$140.50
7 purchase totals =	$914.48		$969.4443	$969.43	$969.35	$969.50