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	$200.47	9.741%	$219.9978	$220.00	$220.00	$220.00
Purchase #2	$146.25	13.431%	$165.8928	$165.89	$165.90	$165.90
Purchase #3	$56.59	9.372%	$61.8936	$61.89	$61.90	$61.90
Purchase #4	$228.91	10.287%	$252.458	$252.46	$252.45	$252.50
Purchase #5	$40.91	12.146%	$45.8789	$45.88	$45.90	$45.90
Purchase #6	$69.57	5.626%	$73.484	$73.48	$73.50	$73.50
Purchase #7	$116.93	6.748%	$124.8204	$124.82	$124.80	$124.80
7 purchase totals =	$859.63		$944.4255	$944.42	$944.45	$944.50