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	$146.28	3.387%	$151.2345	$151.23	$151.25	$151.20
Purchase #2	$76.98	5.723%	$81.3856	$81.39	$81.40	$81.40
Purchase #3	$58.40	9.496%	$63.9457	$63.95	$63.95	$63.90
Purchase #4	$71.98	9.506%	$78.8224	$78.82	$78.80	$78.80
Purchase #5	$30.28	6.170%	$32.1483	$32.15	$32.15	$32.10
Purchase #6	$210.28	11.586%	$234.643	$234.64	$234.65	$234.60
Purchase #7	$37.96	7.630%	$40.8563	$40.86	$40.85	$40.90
7 purchase totals =	$632.16		$683.0358	$683.04	$683.05	$682.90