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	$107.31	8.751%	$116.7007	$116.70	$116.70	$116.70
Purchase #2	$100.67	9.380%	$110.1128	$110.11	$110.10	$110.10
Purchase #3	$71.55	10.618%	$79.1472	$79.15	$79.15	$79.10
Purchase #4	$137.47	6.676%	$146.6475	$146.65	$146.65	$146.60
Purchase #5	$126.41	10.332%	$139.4707	$139.47	$139.45	$139.50
Purchase #6	$157.67	9.471%	$172.6029	$172.60	$172.60	$172.60
Purchase #7	$250.42	12.406%	$281.4871	$281.49	$281.50	$281.50
7 purchase totals =	$951.50		$1,046.1689	$1,046.17	$1,046.15	$1,046.10