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	$117.29	11.788%	$131.1161	$131.12	$131.10	$131.10
Purchase #2	$77.99	6.237%	$82.8542	$82.85	$82.85	$82.90
Purchase #3	$58.96	5.741%	$62.3449	$62.34	$62.35	$62.30
Purchase #4	$184.37	13.778%	$209.7725	$209.77	$209.75	$209.80
Purchase #5	$214.82	4.867%	$225.2753	$225.28	$225.30	$225.30
Purchase #6	$192.59	10.536%	$212.8813	$212.88	$212.90	$212.90
Purchase #7	$130.85	11.155%	$145.4463	$145.45	$145.45	$145.40
7 purchase totals =	$976.87		$1,069.6906	$1,069.69	$1,069.70	$1,069.70