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	$10.29	10.184%	$11.3379	$11.34	$11.35	$11.30
Purchase #2	$61.38	6.729%	$65.5103	$65.51	$65.50	$65.50
Purchase #3	$56.73	10.862%	$62.892	$62.89	$62.90	$62.90
Purchase #4	$34.63	4.505%	$36.1901	$36.19	$36.20	$36.20
Purchase #5	$82.41	9.842%	$90.5208	$90.52	$90.50	$90.50
Purchase #6	$97.79	13.503%	$110.9946	$110.99	$111.00	$111.00
Purchase #7	$40.68	11.266%	$45.263	$45.26	$45.25	$45.30
7 purchase totals =	$383.91		$422.7087	$422.70	$422.70	$422.70