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	$40.89	12.361%	$45.9444	$45.94	$45.95	$45.90
Purchase #2	$83.31	8.591%	$90.4672	$90.47	$90.45	$90.50
Purchase #3	$182.64	11.377%	$203.419	$203.42	$203.40	$203.40
Purchase #4	$77.66	13.699%	$88.2986	$88.30	$88.30	$88.30
Purchase #5	$30.81	7.822%	$33.22	$33.22	$33.20	$33.20
Purchase #6	$209.54	7.468%	$225.1884	$225.19	$225.20	$225.20
Purchase #7	$91.72	6.397%	$97.5873	$97.59	$97.60	$97.60
7 purchase totals =	$716.57		$784.1249	$784.13	$784.10	$784.10