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	$87.32	12.760%	$98.462	$98.46	$98.45	$98.50
Purchase #2	$228.38	11.313%	$254.2166	$254.22	$254.20	$254.20
Purchase #3	$7.54	3.781%	$7.8251	$7.83	$7.85	$7.80
Purchase #4	$132.71	10.181%	$146.2212	$146.22	$146.20	$146.20
Purchase #5	$145.62	3.467%	$150.6686	$150.67	$150.65	$150.70
Purchase #6	$46.44	8.695%	$50.478	$50.48	$50.50	$50.50
Purchase #7	$14.66	6.629%	$15.6318	$15.63	$15.65	$15.60
7 purchase totals =	$662.67		$723.5033	$723.51	$723.50	$723.50