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	$50.25	3.392%	$51.9545	$51.95	$51.95	$52.00
Purchase #2	$11.61	3.669%	$12.036	$12.04	$12.05	$12.00
Purchase #3	$79.44	4.692%	$83.1673	$83.17	$83.15	$83.20
Purchase #4	$86.56	6.760%	$92.4115	$92.41	$92.40	$92.40
Purchase #5	$53.75	10.569%	$59.4308	$59.43	$59.45	$59.40
Purchase #6	$195.71	13.414%	$221.9625	$221.96	$221.95	$222.00
Purchase #7	$183.78	13.590%	$208.7557	$208.76	$208.75	$208.80
7 purchase totals =	$661.10		$729.7183	$729.72	$729.70	$729.80