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	$145.64	8.635%	$158.216	$158.22	$158.20	$158.20
Purchase #2	$97.96	13.580%	$111.263	$111.26	$111.25	$111.30
Purchase #3	$67.49	10.740%	$74.7384	$74.74	$74.75	$74.70
Purchase #4	$111.52	7.529%	$119.9163	$119.92	$119.90	$119.90
Purchase #5	$137.99	12.601%	$155.3781	$155.38	$155.40	$155.40
Purchase #6	$143.59	6.355%	$152.7151	$152.72	$152.70	$152.70
Purchase #7	$49.51	10.512%	$54.7145	$54.71	$54.70	$54.70
7 purchase totals =	$753.70		$826.9414	$826.95	$826.90	$826.90