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	$244.34	4.730%	$255.8973	$255.90	$255.90	$255.90
Purchase #2	$36.64	3.405%	$37.8876	$37.89	$37.90	$37.90
Purchase #3	$28.73	13.262%	$32.5402	$32.54	$32.55	$32.50
Purchase #4	$20.85	11.390%	$23.2248	$23.22	$23.20	$23.20
Purchase #5	$224.78	4.157%	$234.1241	$234.12	$234.10	$234.10
Purchase #6	$122.32	12.730%	$137.8913	$137.89	$137.90	$137.90
Purchase #7	$90.61	5.374%	$95.4794	$95.48	$95.50	$95.50
7 purchase totals =	$768.27		$817.0447	$817.04	$817.05	$817.00