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	$103.36	8.206%	$111.8417	$111.84	$111.85	$111.80
Purchase #2	$78.43	5.476%	$82.7248	$82.72	$82.70	$82.70
Purchase #3	$36.42	9.763%	$39.9757	$39.98	$40.00	$40.00
Purchase #4	$209.52	7.691%	$225.6342	$225.63	$225.65	$225.60
Purchase #5	$9.78	4.465%	$10.2167	$10.22	$10.20	$10.20
Purchase #6	$48.98	3.242%	$50.5679	$50.57	$50.55	$50.60
Purchase #7	$90.89	4.526%	$95.0037	$95.00	$95.00	$95.00
7 purchase totals =	$577.38		$615.9647	$615.96	$615.95	$615.90