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	$164.51	6.537%	$175.264	$175.26	$175.25	$175.30
Purchase #2	$155.93	9.158%	$170.2101	$170.21	$170.20	$170.20
Purchase #3	$184.89	4.327%	$192.8902	$192.89	$192.90	$192.90
Purchase #4	$79.50	13.866%	$90.5235	$90.52	$90.50	$90.50
Purchase #5	$149.92	10.387%	$165.4922	$165.49	$165.50	$165.50
Purchase #6	$237.84	10.459%	$262.7157	$262.72	$262.70	$262.70
Purchase #7	$193.75	11.759%	$216.5331	$216.53	$216.55	$216.50
7 purchase totals =	$1,166.34		$1,273.6288	$1,273.62	$1,273.60	$1,273.60