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	$178.43	11.817%	$199.5151	$199.52	$199.50	$199.50
Purchase #2	$128.32	4.548%	$134.156	$134.16	$134.15	$134.20
Purchase #3	$89.51	3.740%	$92.8577	$92.86	$92.85	$92.90
Purchase #4	$187.33	13.456%	$212.5371	$212.54	$212.55	$212.50
Purchase #5	$206.68	10.842%	$229.0882	$229.09	$229.10	$229.10
Purchase #6	$209.31	7.810%	$225.6571	$225.66	$225.65	$225.70
Purchase #7	$160.25	6.527%	$170.7095	$170.71	$170.70	$170.70
7 purchase totals =	$1,159.83		$1,264.5207	$1,264.54	$1,264.50	$1,264.60