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	$92.36	4.103%	$96.1495	$96.15	$96.15	$96.10
Purchase #2	$64.73	4.518%	$67.6545	$67.65	$67.65	$67.70
Purchase #3	$36.42	5.614%	$38.4646	$38.46	$38.45	$38.50
Purchase #4	$165.49	10.871%	$183.4804	$183.48	$183.50	$183.50
Purchase #5	$244.60	4.634%	$255.9348	$255.93	$255.95	$255.90
Purchase #6	$146.41	4.621%	$153.1756	$153.18	$153.20	$153.20
Purchase #7	$55.46	4.609%	$58.0162	$58.02	$58.00	$58.00
7 purchase totals =	$805.47		$852.8756	$852.87	$852.90	$852.90