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	$86.56	11.778%	$96.755	$96.76	$96.75	$96.80
Purchase #2	$161.88	12.356%	$181.8819	$181.88	$181.90	$181.90
Purchase #3	$103.83	7.124%	$111.2268	$111.23	$111.25	$111.20
Purchase #4	$234.75	5.325%	$247.2504	$247.25	$247.25	$247.30
Purchase #5	$18.43	4.227%	$19.209	$19.21	$19.20	$19.20
Purchase #6	$159.80	4.181%	$166.4812	$166.48	$166.50	$166.50
Purchase #7	$58.67	4.575%	$61.3542	$61.35	$61.35	$61.40
7 purchase totals =	$823.92		$884.1585	$884.16	$884.20	$884.30