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	$111.61	5.119%	$117.3233	$117.32	$117.30	$117.30
Purchase #2	$89.93	3.114%	$92.7304	$92.73	$92.75	$92.70
Purchase #3	$129.87	11.422%	$144.7038	$144.70	$144.70	$144.70
Purchase #4	$237.77	5.215%	$250.1697	$250.17	$250.15	$250.20
Purchase #5	$76.95	10.606%	$85.1113	$85.11	$85.10	$85.10
Purchase #6	$180.58	10.793%	$200.07	$200.07	$200.05	$200.10
Purchase #7	$165.95	4.776%	$173.8758	$173.88	$173.90	$173.90
7 purchase totals =	$992.66		$1,063.9843	$1,063.98	$1,063.95	$1,064.00