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	$130.76	10.358%	$144.3041	$144.30	$144.30	$144.30
Purchase #2	$189.93	8.309%	$205.7113	$205.71	$205.70	$205.70
Purchase #3	$172.81	7.108%	$185.0933	$185.09	$185.10	$185.10
Purchase #4	$75.89	9.872%	$83.3819	$83.38	$83.40	$83.40
Purchase #5	$232.25	11.153%	$258.1528	$258.15	$258.15	$258.20
Purchase #6	$33.89	10.110%	$37.3163	$37.32	$37.30	$37.30
Purchase #7	$129.76	7.793%	$139.8722	$139.87	$139.85	$139.90
7 purchase totals =	$965.29		$1,053.8319	$1,053.82	$1,053.80	$1,053.90