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	$37.41	7.863%	$40.3515	$40.35	$40.35	$40.40
Purchase #2	$18.42	11.521%	$20.5422	$20.54	$20.55	$20.50
Purchase #3	$189.70	11.306%	$211.1475	$211.15	$211.15	$211.10
Purchase #4	$233.39	13.652%	$265.2524	$265.25	$265.25	$265.30
Purchase #5	$127.46	10.640%	$141.0217	$141.02	$141.00	$141.00
Purchase #6	$144.81	4.352%	$151.1121	$151.11	$151.10	$151.10
Purchase #7	$213.38	8.535%	$231.592	$231.59	$231.60	$231.60
7 purchase totals =	$964.57		$1,061.0194	$1,061.01	$1,061.00	$1,061.00