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	$144.80	7.361%	$155.4587	$155.46	$155.45	$155.50
Purchase #2	$61.92	13.339%	$70.1795	$70.18	$70.20	$70.20
Purchase #3	$40.95	10.571%	$45.2788	$45.28	$45.30	$45.30
Purchase #4	$121.59	4.287%	$126.8026	$126.80	$126.80	$126.80
Purchase #5	$65.99	9.843%	$72.4854	$72.49	$72.50	$72.50
Purchase #6	$209.47	7.253%	$224.6629	$224.66	$224.65	$224.70
Purchase #7	$37.45	7.589%	$40.2921	$40.29	$40.30	$40.30
7 purchase totals =	$682.17		$735.1600	$735.16	$735.20	$735.30