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	$57.28	8.119%	$61.9306	$61.93	$61.95	$61.90
Purchase #2	$59.71	11.807%	$66.76	$66.76	$66.75	$66.80
Purchase #3	$30.34	10.715%	$33.5909	$33.59	$33.60	$33.60
Purchase #4	$42.40	7.328%	$45.5071	$45.51	$45.50	$45.50
Purchase #5	$197.35	10.366%	$217.8073	$217.81	$217.80	$217.80
Purchase #6	$9.58	6.787%	$10.2302	$10.23	$10.25	$10.20
Purchase #7	$190.67	4.741%	$199.7097	$199.71	$199.70	$199.70
7 purchase totals =	$587.33		$635.5358	$635.54	$635.55	$635.50