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	$63.72	4.629%	$66.6696	$66.67	$66.65	$66.70
Purchase #2	$134.45	12.447%	$151.185	$151.19	$151.20	$151.20
Purchase #3	$79.58	3.388%	$82.2762	$82.28	$82.30	$82.30
Purchase #4	$37.54	8.188%	$40.6138	$40.61	$40.60	$40.60
Purchase #5	$156.63	5.777%	$165.6785	$165.68	$165.70	$165.70
Purchase #6	$179.33	3.460%	$185.5348	$185.53	$185.55	$185.50
Purchase #7	$89.93	13.258%	$101.8529	$101.85	$101.85	$101.90
7 purchase totals =	$741.18		$793.8108	$793.81	$793.85	$793.90