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	$218.72	4.284%	$228.09	$228.09	$228.10	$228.10
Purchase #2	$140.59	8.485%	$152.5191	$152.52	$152.50	$152.50
Purchase #3	$151.94	9.530%	$166.4199	$166.42	$166.40	$166.40
Purchase #4	$145.64	11.131%	$161.8512	$161.85	$161.85	$161.90
Purchase #5	$73.47	6.363%	$78.1449	$78.14	$78.15	$78.10
Purchase #6	$220.98	12.220%	$247.9838	$247.98	$248.00	$248.00
Purchase #7	$84.30	13.291%	$95.5043	$95.50	$95.50	$95.50
7 purchase totals =	$1,035.64		$1,130.5132	$1,130.50	$1,130.50	$1,130.50