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	$157.25	11.702%	$175.6514	$175.65	$175.65	$175.70
Purchase #2	$99.32	11.827%	$111.0666	$111.07	$111.05	$111.10
Purchase #3	$20.27	3.531%	$20.9857	$20.99	$21.00	$21.00
Purchase #4	$248.80	4.646%	$260.3592	$260.36	$260.35	$260.40
Purchase #5	$182.54	5.111%	$191.8696	$191.87	$191.85	$191.90
Purchase #6	$26.82	8.376%	$29.0664	$29.07	$29.05	$29.10
Purchase #7	$35.72	5.547%	$37.7014	$37.70	$37.70	$37.70
7 purchase totals =	$770.72		$826.7003	$826.71	$826.65	$826.90