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	$190.26	13.793%	$216.5026	$216.50	$216.50	$216.50
Purchase #2	$89.62	11.724%	$100.127	$100.13	$100.15	$100.10
Purchase #3	$140.52	13.338%	$159.2626	$159.26	$159.25	$159.30
Purchase #4	$191.47	6.690%	$204.2793	$204.28	$204.30	$204.30
Purchase #5	$204.94	11.178%	$227.8482	$227.85	$227.85	$227.80
Purchase #6	$159.69	3.769%	$165.7087	$165.71	$165.70	$165.70
Purchase #7	$217.63	4.588%	$227.6149	$227.61	$227.60	$227.60
7 purchase totals =	$1,194.13		$1,301.3433	$1,301.34	$1,301.35	$1,301.30