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	$219.74	3.671%	$227.8067	$227.81	$227.80	$227.80
Purchase #2	$157.32	9.488%	$172.2465	$172.25	$172.25	$172.20
Purchase #3	$33.54	10.413%	$37.0325	$37.03	$37.05	$37.00
Purchase #4	$231.88	8.315%	$251.1608	$251.16	$251.15	$251.20
Purchase #5	$93.31	11.810%	$104.3299	$104.33	$104.35	$104.30
Purchase #6	$85.88	10.343%	$94.7626	$94.76	$94.75	$94.80
Purchase #7	$41.55	11.609%	$46.3735	$46.37	$46.35	$46.40
7 purchase totals =	$863.22		$933.7125	$933.71	$933.70	$933.70