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	$220.51	4.148%	$229.6568	$229.66	$229.65	$229.70
Purchase #2	$219.86	8.503%	$238.5547	$238.55	$238.55	$238.60
Purchase #3	$62.77	5.594%	$66.2814	$66.28	$66.30	$66.30
Purchase #4	$229.97	11.598%	$256.6419	$256.64	$256.65	$256.60
Purchase #5	$39.80	3.340%	$41.1293	$41.13	$41.15	$41.10
Purchase #6	$18.28	11.215%	$20.3301	$20.33	$20.35	$20.30
Purchase #7	$183.61	5.806%	$194.2704	$194.27	$194.25	$194.30
7 purchase totals =	$974.80		$1,046.8646	$1,046.86	$1,046.90	$1,046.90