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	$247.60	6.102%	$262.7086	$262.71	$262.70	$262.70
Purchase #2	$43.59	6.275%	$46.3253	$46.33	$46.35	$46.30
Purchase #3	$105.93	9.847%	$116.3609	$116.36	$116.35	$116.40
Purchase #4	$248.63	10.805%	$275.4945	$275.49	$275.50	$275.50
Purchase #5	$179.35	7.255%	$192.3618	$192.36	$192.35	$192.40
Purchase #6	$101.81	9.495%	$111.4769	$111.48	$111.50	$111.50
Purchase #7	$159.73	9.698%	$175.2206	$175.22	$175.20	$175.20
7 purchase totals =	$1,086.64		$1,179.9486	$1,179.95	$1,179.95	$1,180.00