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	$102.52	8.561%	$111.2967	$111.30	$111.30	$111.30
Purchase #2	$130.29	9.186%	$142.2584	$142.26	$142.25	$142.30
Purchase #3	$151.65	10.259%	$167.2078	$167.21	$167.20	$167.20
Purchase #4	$17.51	6.453%	$18.6399	$18.64	$18.65	$18.60
Purchase #5	$155.63	11.709%	$173.8527	$173.85	$173.85	$173.90
Purchase #6	$27.80	13.390%	$31.5224	$31.52	$31.50	$31.50
Purchase #7	$125.48	4.180%	$130.7251	$130.73	$130.75	$130.70
7 purchase totals =	$710.88		$775.5030	$775.51	$775.50	$775.50