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	$211.25	8.330%	$228.8471	$228.85	$228.85	$228.80
Purchase #2	$60.52	10.290%	$66.7475	$66.75	$66.75	$66.70
Purchase #3	$243.55	13.471%	$276.3586	$276.36	$276.35	$276.40
Purchase #4	$18.50	10.200%	$20.387	$20.39	$20.40	$20.40
Purchase #5	$53.52	10.451%	$59.1134	$59.11	$59.10	$59.10
Purchase #6	$40.73	5.418%	$42.9368	$42.94	$42.95	$42.90
Purchase #7	$200.50	11.138%	$222.8317	$222.83	$222.85	$222.80
7 purchase totals =	$828.57		$917.2221	$917.23	$917.25	$917.10