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	$157.77	9.817%	$173.2583	$173.26	$173.25	$173.30
Purchase #2	$92.88	13.298%	$105.2312	$105.23	$105.25	$105.20
Purchase #3	$77.55	6.111%	$82.2891	$82.29	$82.30	$82.30
Purchase #4	$189.53	10.332%	$209.1122	$209.11	$209.10	$209.10
Purchase #5	$234.94	6.481%	$250.1665	$250.17	$250.15	$250.20
Purchase #6	$87.98	5.624%	$92.928	$92.93	$92.95	$92.90
Purchase #7	$136.98	13.334%	$155.2449	$155.24	$155.25	$155.20
7 purchase totals =	$977.63		$1,068.2302	$1,068.23	$1,068.25	$1,068.20