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	$37.68	10.204%	$41.5249	$41.52	$41.50	$41.50
Purchase #2	$157.86	11.155%	$175.4693	$175.47	$175.45	$175.50
Purchase #3	$67.65	5.269%	$71.2145	$71.21	$71.20	$71.20
Purchase #4	$78.93	6.104%	$83.7479	$83.75	$83.75	$83.70
Purchase #5	$119.67	10.268%	$131.9577	$131.96	$131.95	$132.00
Purchase #6	$49.93	10.415%	$55.1302	$55.13	$55.15	$55.10
Purchase #7	$229.44	11.604%	$256.0642	$256.06	$256.05	$256.10
7 purchase totals =	$741.16		$815.1087	$815.10	$815.05	$815.10