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	$11.31	5.816%	$11.9678	$11.97	$11.95	$12.00
Purchase #2	$223.43	4.812%	$234.1815	$234.18	$234.20	$234.20
Purchase #3	$156.70	12.227%	$175.8597	$175.86	$175.85	$175.90
Purchase #4	$186.91	5.127%	$196.4929	$196.49	$196.50	$196.50
Purchase #5	$20.41	8.476%	$22.14	$22.14	$22.15	$22.10
Purchase #6	$244.93	13.778%	$278.6765	$278.68	$278.70	$278.70
Purchase #7	$81.90	11.739%	$91.5142	$91.51	$91.50	$91.50
7 purchase totals =	$925.59		$1,010.8326	$1,010.83	$1,010.85	$1,010.90