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	$60.58	10.778%	$67.1093	$67.11	$67.10	$67.10
Purchase #2	$83.34	6.761%	$88.9746	$88.97	$88.95	$89.00
Purchase #3	$142.46	4.441%	$148.7866	$148.79	$148.80	$148.80
Purchase #4	$185.55	9.671%	$203.4945	$203.49	$203.50	$203.50
Purchase #5	$191.38	13.817%	$217.823	$217.82	$217.80	$217.80
Purchase #6	$40.41	3.654%	$41.8866	$41.89	$41.90	$41.90
Purchase #7	$154.60	11.399%	$172.2229	$172.22	$172.20	$172.20
7 purchase totals =	$858.32		$940.2975	$940.29	$940.25	$940.30