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	$179.58	9.472%	$196.5898	$196.59	$196.60	$196.60
Purchase #2	$248.79	13.470%	$282.302	$282.30	$282.30	$282.30
Purchase #3	$160.45	3.224%	$165.6229	$165.62	$165.60	$165.60
Purchase #4	$58.95	6.577%	$62.8271	$62.83	$62.85	$62.80
Purchase #5	$67.89	10.634%	$75.1094	$75.11	$75.10	$75.10
Purchase #6	$161.31	7.377%	$173.2098	$173.21	$173.20	$173.20
Purchase #7	$19.52	6.762%	$20.8399	$20.84	$20.85	$20.80
7 purchase totals =	$896.49		$976.5009	$976.50	$976.50	$976.40