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	$64.51	11.336%	$71.8229	$71.82	$71.80	$71.80
Purchase #2	$38.75	11.600%	$43.245	$43.25	$43.25	$43.20
Purchase #3	$15.98	9.576%	$17.5102	$17.51	$17.50	$17.50
Purchase #4	$119.27	12.459%	$134.1298	$134.13	$134.15	$134.10
Purchase #5	$75.25	13.860%	$85.6797	$85.68	$85.70	$85.70
Purchase #6	$173.97	9.224%	$190.017	$190.02	$190.00	$190.00
Purchase #7	$79.62	7.250%	$85.3925	$85.39	$85.40	$85.40
7 purchase totals =	$567.35		$627.7971	$627.80	$627.80	$627.70