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	$60.58	8.157%	$65.5215	$65.52	$65.50	$65.50
Purchase #2	$22.81	10.619%	$25.2322	$25.23	$25.25	$25.20
Purchase #3	$101.91	3.589%	$105.5675	$105.57	$105.55	$105.60
Purchase #4	$148.90	4.242%	$155.2163	$155.22	$155.20	$155.20
Purchase #5	$92.39	8.756%	$100.4797	$100.48	$100.50	$100.50
Purchase #6	$30.66	10.561%	$33.898	$33.90	$33.90	$33.90
Purchase #7	$228.47	9.682%	$250.5905	$250.59	$250.60	$250.60
7 purchase totals =	$685.72		$736.5057	$736.51	$736.50	$736.50