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	$194.91	7.684%	$209.8869	$209.89	$209.90	$209.90
Purchase #2	$151.42	13.559%	$171.951	$171.95	$171.95	$172.00
Purchase #3	$83.97	12.333%	$94.326	$94.33	$94.35	$94.30
Purchase #4	$137.72	9.198%	$150.3875	$150.39	$150.40	$150.40
Purchase #5	$241.34	3.499%	$249.7845	$249.78	$249.80	$249.80
Purchase #6	$139.53	8.680%	$151.6412	$151.64	$151.65	$151.60
Purchase #7	$160.97	12.754%	$181.5001	$181.50	$181.50	$181.50
7 purchase totals =	$1,109.86		$1,209.4772	$1,209.48	$1,209.55	$1,209.50