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	$147.70	5.430%	$155.7201	$155.72	$155.70	$155.70
Purchase #2	$63.89	4.571%	$66.8104	$66.81	$66.80	$66.80
Purchase #3	$151.56	10.431%	$167.3692	$167.37	$167.35	$167.40
Purchase #4	$217.90	7.284%	$233.7718	$233.77	$233.75	$233.80
Purchase #5	$244.98	12.629%	$275.9185	$275.92	$275.90	$275.90
Purchase #6	$211.90	4.781%	$222.0309	$222.03	$222.05	$222.00
Purchase #7	$117.74	12.435%	$132.381	$132.38	$132.40	$132.40
7 purchase totals =	$1,155.67		$1,254.0019	$1,254.00	$1,253.95	$1,254.00