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	$235.95	7.279%	$253.1248	$253.12	$253.10	$253.10
Purchase #2	$16.36	9.133%	$17.8542	$17.85	$17.85	$17.90
Purchase #3	$76.83	7.532%	$82.6168	$82.62	$82.60	$82.60
Purchase #4	$172.79	5.489%	$182.2744	$182.27	$182.25	$182.30
Purchase #5	$64.29	4.333%	$67.0757	$67.08	$67.10	$67.10
Purchase #6	$149.91	5.778%	$158.5718	$158.57	$158.55	$158.60
Purchase #7	$52.91	11.657%	$59.0777	$59.08	$59.10	$59.10
7 purchase totals =	$769.04		$820.5954	$820.59	$820.55	$820.70