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	$99.37	9.120%	$108.4325	$108.43	$108.45	$108.40
Purchase #2	$208.56	5.837%	$220.7336	$220.73	$220.75	$220.70
Purchase #3	$244.67	3.594%	$253.4634	$253.46	$253.45	$253.50
Purchase #4	$209.78	8.862%	$228.3707	$228.37	$228.35	$228.40
Purchase #5	$10.69	5.670%	$11.2961	$11.30	$11.30	$11.30
Purchase #6	$137.33	5.419%	$144.7719	$144.77	$144.75	$144.80
Purchase #7	$135.72	11.492%	$151.3169	$151.32	$151.30	$151.30
7 purchase totals =	$1,046.12		$1,118.3851	$1,118.38	$1,118.35	$1,118.40