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	$39.48	10.217%	$43.5137	$43.51	$43.50	$43.50
Purchase #2	$245.48	4.237%	$255.881	$255.88	$255.90	$255.90
Purchase #3	$228.55	11.518%	$254.8744	$254.87	$254.85	$254.90
Purchase #4	$149.40	7.257%	$160.242	$160.24	$160.25	$160.20
Purchase #5	$58.53	10.152%	$64.472	$64.47	$64.45	$64.50
Purchase #6	$100.80	7.390%	$108.2491	$108.25	$108.25	$108.20
Purchase #7	$37.54	10.202%	$41.3698	$41.37	$41.35	$41.40
7 purchase totals =	$859.78		$928.6020	$928.59	$928.55	$928.60