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	$135.43	11.527%	$151.041	$151.04	$151.05	$151.00
Purchase #2	$105.43	5.684%	$111.4226	$111.42	$111.40	$111.40
Purchase #3	$126.70	10.105%	$139.503	$139.50	$139.50	$139.50
Purchase #4	$204.58	12.515%	$230.1832	$230.18	$230.20	$230.20
Purchase #5	$208.73	9.152%	$227.833	$227.83	$227.85	$227.80
Purchase #6	$59.81	10.219%	$65.922	$65.92	$65.90	$65.90
Purchase #7	$97.76	11.528%	$109.0298	$109.03	$109.05	$109.00
7 purchase totals =	$938.44		$1,034.9346	$1,034.92	$1,034.95	$1,034.80