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	$93.74	11.457%	$104.4798	$104.48	$104.50	$104.50
Purchase #2	$82.71	9.231%	$90.345	$90.35	$90.35	$90.30
Purchase #3	$79.71	5.318%	$83.949	$83.95	$83.95	$83.90
Purchase #4	$50.57	11.163%	$56.2151	$56.22	$56.20	$56.20
Purchase #5	$199.74	12.845%	$225.3966	$225.40	$225.40	$225.40
Purchase #6	$61.34	8.744%	$66.7036	$66.70	$66.70	$66.70
Purchase #7	$204.50	11.846%	$228.7251	$228.73	$228.75	$228.70
7 purchase totals =	$772.31		$855.8142	$855.83	$855.85	$855.70