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	$69.29	13.249%	$78.4702	$78.47	$78.45	$78.50
Purchase #2	$228.79	9.369%	$250.2253	$250.23	$250.25	$250.20
Purchase #3	$47.72	6.713%	$50.9234	$50.92	$50.90	$50.90
Purchase #4	$43.72	13.844%	$49.7726	$49.77	$49.75	$49.80
Purchase #5	$29.39	11.680%	$32.8228	$32.82	$32.80	$32.80
Purchase #6	$250.57	5.698%	$264.8475	$264.85	$264.85	$264.80
Purchase #7	$214.48	5.162%	$225.5515	$225.55	$225.55	$225.60
7 purchase totals =	$883.96		$952.6133	$952.61	$952.55	$952.60