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	$50.95	4.718%	$53.3538	$53.35	$53.35	$53.40
Purchase #2	$38.46	3.222%	$39.6992	$39.70	$39.70	$39.70
Purchase #3	$42.71	7.409%	$45.8744	$45.87	$45.85	$45.90
Purchase #4	$46.96	11.503%	$52.3618	$52.36	$52.35	$52.40
Purchase #5	$199.51	3.497%	$206.4869	$206.49	$206.50	$206.50
Purchase #6	$40.72	9.257%	$44.4895	$44.49	$44.50	$44.50
Purchase #7	$205.34	7.414%	$220.5639	$220.56	$220.55	$220.60
7 purchase totals =	$624.65		$662.8295	$662.82	$662.80	$663.00