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	$214.97	3.497%	$222.4875	$222.49	$222.50	$222.50
Purchase #2	$105.41	5.452%	$111.157	$111.16	$111.15	$111.20
Purchase #3	$55.58	7.625%	$59.818	$59.82	$59.80	$59.80
Purchase #4	$21.56	4.168%	$22.4586	$22.46	$22.45	$22.50
Purchase #5	$88.76	7.527%	$95.441	$95.44	$95.45	$95.40
Purchase #6	$19.80	10.294%	$21.8382	$21.84	$21.85	$21.80
Purchase #7	$156.76	8.689%	$170.3809	$170.38	$170.40	$170.40
7 purchase totals =	$662.84		$703.5812	$703.59	$703.60	$703.60