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	$173.29	12.706%	$195.3082	$195.31	$195.30	$195.30
Purchase #2	$50.98	4.150%	$53.0957	$53.10	$53.10	$53.10
Purchase #3	$124.32	10.683%	$137.6011	$137.60	$137.60	$137.60
Purchase #4	$115.53	7.795%	$124.5356	$124.54	$124.55	$124.50
Purchase #5	$78.71	11.383%	$87.6696	$87.67	$87.65	$87.70
Purchase #6	$101.58	9.539%	$111.2697	$111.27	$111.25	$111.30
Purchase #7	$68.82	13.171%	$77.8843	$77.88	$77.90	$77.90
7 purchase totals =	$713.23		$787.3642	$787.37	$787.35	$787.40