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	$172.45	10.485%	$190.5314	$190.53	$190.55	$190.50
Purchase #2	$53.75	11.237%	$59.7899	$59.79	$59.80	$59.80
Purchase #3	$23.78	7.693%	$25.6094	$25.61	$25.60	$25.60
Purchase #4	$200.70	13.833%	$228.4628	$228.46	$228.45	$228.50
Purchase #5	$76.39	3.429%	$79.0094	$79.01	$79.00	$79.00
Purchase #6	$195.32	8.787%	$212.4828	$212.48	$212.50	$212.50
Purchase #7	$57.93	6.388%	$61.6306	$61.63	$61.65	$61.60
7 purchase totals =	$780.32		$857.5163	$857.51	$857.55	$857.50