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	$175.56	8.801%	$191.011	$191.01	$191.00	$191.00
Purchase #2	$6.89	9.142%	$7.5199	$7.52	$7.50	$7.50
Purchase #3	$132.65	9.842%	$145.7054	$145.71	$145.70	$145.70
Purchase #4	$36.58	9.370%	$40.0075	$40.01	$40.00	$40.00
Purchase #5	$213.86	3.873%	$222.1428	$222.14	$222.15	$222.10
Purchase #6	$128.74	6.586%	$137.2188	$137.22	$137.20	$137.20
Purchase #7	$20.79	9.258%	$22.7147	$22.71	$22.70	$22.70
7 purchase totals =	$715.07		$766.3201	$766.32	$766.25	$766.20