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	$238.34	3.681%	$247.1133	$247.11	$247.10	$247.10
Purchase #2	$84.66	7.428%	$90.9485	$90.95	$90.95	$90.90
Purchase #3	$6.89	8.694%	$7.489	$7.49	$7.50	$7.50
Purchase #4	$101.86	9.800%	$111.8423	$111.84	$111.85	$111.80
Purchase #5	$226.82	6.133%	$240.7309	$240.73	$240.75	$240.70
Purchase #6	$55.83	11.835%	$62.4375	$62.44	$62.45	$62.40
Purchase #7	$207.94	13.267%	$235.5274	$235.53	$235.55	$235.50
7 purchase totals =	$922.34		$996.0889	$996.09	$996.15	$995.90