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	$229.91	10.548%	$254.1609	$254.16	$254.15	$254.20
Purchase #2	$147.34	3.857%	$153.0229	$153.02	$153.00	$153.00
Purchase #3	$79.58	12.313%	$89.3787	$89.38	$89.40	$89.40
Purchase #4	$241.68	5.170%	$254.1749	$254.17	$254.15	$254.20
Purchase #5	$34.52	4.645%	$36.1235	$36.12	$36.10	$36.10
Purchase #6	$152.27	4.755%	$159.5104	$159.51	$159.50	$159.50
Purchase #7	$151.47	13.203%	$171.4686	$171.47	$171.45	$171.50
7 purchase totals =	$1,036.77		$1,117.8399	$1,117.83	$1,117.75	$1,117.90