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	$88.65	13.254%	$100.3997	$100.40	$100.40	$100.40
Purchase #2	$222.91	4.705%	$233.3979	$233.40	$233.40	$233.40
Purchase #3	$108.34	4.757%	$113.4937	$113.49	$113.50	$113.50
Purchase #4	$65.41	9.160%	$71.4016	$71.40	$71.40	$71.40
Purchase #5	$188.73	9.500%	$206.6594	$206.66	$206.65	$206.70
Purchase #6	$191.84	7.604%	$206.4275	$206.43	$206.45	$206.40
Purchase #7	$89.79	11.711%	$100.3053	$100.31	$100.30	$100.30
7 purchase totals =	$955.67		$1,032.0851	$1,032.09	$1,032.10	$1,032.10