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	$154.67	11.740%	$172.8283	$172.83	$172.85	$172.80
Purchase #2	$37.87	10.560%	$41.8691	$41.87	$41.85	$41.90
Purchase #3	$193.68	12.808%	$218.4865	$218.49	$218.50	$218.50
Purchase #4	$238.55	4.352%	$248.9317	$248.93	$248.95	$248.90
Purchase #5	$95.74	4.155%	$99.718	$99.72	$99.70	$99.70
Purchase #6	$131.91	13.306%	$149.4619	$149.46	$149.45	$149.50
Purchase #7	$132.73	3.611%	$137.5229	$137.52	$137.50	$137.50
7 purchase totals =	$985.15		$1,068.8184	$1,068.82	$1,068.80	$1,068.80