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	$60.64	11.175%	$67.4165	$67.42	$67.40	$67.40
Purchase #2	$52.46	3.828%	$54.4682	$54.47	$54.45	$54.50
Purchase #3	$236.44	9.485%	$258.8663	$258.87	$258.85	$258.90
Purchase #4	$37.60	10.331%	$41.4845	$41.48	$41.50	$41.50
Purchase #5	$136.60	9.415%	$149.4609	$149.46	$149.45	$149.50
Purchase #6	$205.45	6.851%	$219.5254	$219.53	$219.55	$219.50
Purchase #7	$67.62	5.583%	$71.3952	$71.40	$71.40	$71.40
7 purchase totals =	$796.81		$862.6170	$862.63	$862.60	$862.70