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	$82.65	12.386%	$92.887	$92.89	$92.90	$92.90
Purchase #2	$176.76	6.755%	$188.7001	$188.70	$188.70	$188.70
Purchase #3	$125.55	5.278%	$132.1765	$132.18	$132.20	$132.20
Purchase #4	$52.49	9.164%	$57.3002	$57.30	$57.30	$57.30
Purchase #5	$94.90	11.346%	$105.6674	$105.67	$105.65	$105.70
Purchase #6	$230.90	10.249%	$254.5649	$254.56	$254.55	$254.60
Purchase #7	$246.91	3.463%	$255.4605	$255.46	$255.45	$255.50
7 purchase totals =	$1,010.16		$1,086.7566	$1,086.76	$1,086.75	$1,086.90