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	$75.96	7.244%	$81.4625	$81.46	$81.45	$81.50
Purchase #2	$172.87	10.756%	$191.4639	$191.46	$191.45	$191.50
Purchase #3	$161.33	10.834%	$178.8085	$178.81	$178.80	$178.80
Purchase #4	$119.47	6.813%	$127.6095	$127.61	$127.60	$127.60
Purchase #5	$186.43	5.496%	$196.6762	$196.68	$196.70	$196.70
Purchase #6	$82.41	5.726%	$87.1288	$87.13	$87.15	$87.10
Purchase #7	$43.30	10.160%	$47.6993	$47.70	$47.70	$47.70
7 purchase totals =	$841.77		$910.8487	$910.85	$910.85	$910.90