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	$137.32	3.294%	$141.8433	$141.84	$141.85	$141.80
Purchase #2	$118.50	7.463%	$127.3437	$127.34	$127.35	$127.30
Purchase #3	$91.28	8.625%	$99.1529	$99.15	$99.15	$99.20
Purchase #4	$96.57	13.207%	$109.324	$109.32	$109.30	$109.30
Purchase #5	$116.69	8.444%	$126.5433	$126.54	$126.55	$126.50
Purchase #6	$155.96	11.220%	$173.4587	$173.46	$173.45	$173.50
Purchase #7	$184.84	10.313%	$203.9025	$203.90	$203.90	$203.90
7 purchase totals =	$901.16		$981.5684	$981.55	$981.55	$981.50