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	$44.25	8.578%	$48.0458	$48.05	$48.05	$48.00
Purchase #2	$60.86	8.415%	$65.9814	$65.98	$66.00	$66.00
Purchase #3	$205.39	5.480%	$216.6454	$216.65	$216.65	$216.60
Purchase #4	$26.54	7.225%	$28.4575	$28.46	$28.45	$28.50
Purchase #5	$168.36	3.629%	$174.4698	$174.47	$174.45	$174.50
Purchase #6	$58.42	5.308%	$61.5209	$61.52	$61.50	$61.50
Purchase #7	$69.61	11.160%	$77.3785	$77.38	$77.40	$77.40
7 purchase totals =	$633.43		$672.4993	$672.51	$672.50	$672.50