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	$168.29	5.323%	$177.2481	$177.25	$177.25	$177.20
Purchase #2	$40.69	7.199%	$43.6193	$43.62	$43.60	$43.60
Purchase #3	$49.86	9.647%	$54.67	$54.67	$54.65	$54.70
Purchase #4	$63.85	12.472%	$71.8134	$71.81	$71.80	$71.80
Purchase #5	$98.67	7.180%	$105.7545	$105.75	$105.75	$105.80
Purchase #6	$203.85	9.475%	$223.1648	$223.16	$223.15	$223.20
Purchase #7	$59.93	5.541%	$63.2507	$63.25	$63.25	$63.30
7 purchase totals =	$685.14		$739.5208	$739.51	$739.45	$739.60