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	$152.53	4.808%	$159.8636	$159.86	$159.85	$159.90
Purchase #2	$197.83	13.555%	$224.6459	$224.65	$224.65	$224.60
Purchase #3	$96.42	4.673%	$100.9257	$100.93	$100.95	$100.90
Purchase #4	$54.41	5.121%	$57.1963	$57.20	$57.20	$57.20
Purchase #5	$89.86	11.173%	$99.9001	$99.90	$99.90	$99.90
Purchase #6	$66.62	12.535%	$74.9708	$74.97	$74.95	$75.00
Purchase #7	$246.56	5.225%	$259.4428	$259.44	$259.45	$259.40
7 purchase totals =	$904.23		$976.9452	$976.95	$976.95	$976.90