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	$69.75	3.148%	$71.9457	$71.95	$71.95	$71.90
Purchase #2	$144.95	4.732%	$151.809	$151.81	$151.80	$151.80
Purchase #3	$50.75	4.778%	$53.1748	$53.17	$53.15	$53.20
Purchase #4	$89.63	3.168%	$92.4695	$92.47	$92.45	$92.50
Purchase #5	$34.54	5.369%	$36.3945	$36.39	$36.40	$36.40
Purchase #6	$30.37	5.283%	$31.9744	$31.97	$31.95	$32.00
Purchase #7	$95.77	10.559%	$105.8824	$105.88	$105.90	$105.90
7 purchase totals =	$515.76		$543.6503	$543.64	$543.60	$543.70