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	$227.25	6.448%	$241.9031	$241.90	$241.90	$241.90
Purchase #2	$165.71	11.612%	$184.9522	$184.95	$184.95	$185.00
Purchase #3	$200.53	7.141%	$214.8498	$214.85	$214.85	$214.80
Purchase #4	$76.92	13.693%	$87.4527	$87.45	$87.45	$87.50
Purchase #5	$71.86	3.203%	$74.1617	$74.16	$74.15	$74.20
Purchase #6	$114.85	13.591%	$130.4593	$130.46	$130.45	$130.50
Purchase #7	$178.38	6.299%	$189.6162	$189.62	$189.60	$189.60
7 purchase totals =	$1,035.50		$1,123.3950	$1,123.39	$1,123.35	$1,123.50