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	$88.47	9.112%	$96.5314	$96.53	$96.55	$96.50
Purchase #2	$180.81	10.251%	$199.3448	$199.34	$199.35	$199.30
Purchase #3	$230.31	5.298%	$242.5118	$242.51	$242.50	$242.50
Purchase #4	$16.73	10.399%	$18.4698	$18.47	$18.45	$18.50
Purchase #5	$230.48	13.114%	$260.7051	$260.71	$260.70	$260.70
Purchase #6	$157.25	9.290%	$171.8585	$171.86	$171.85	$171.90
Purchase #7	$40.34	13.464%	$45.7714	$45.77	$45.75	$45.80
7 purchase totals =	$944.39		$1,035.1928	$1,035.19	$1,035.15	$1,035.20