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	$43.90	4.479%	$45.8663	$45.87	$45.85	$45.90
Purchase #2	$216.61	12.651%	$244.0133	$244.01	$244.00	$244.00
Purchase #3	$227.31	12.846%	$256.5102	$256.51	$256.50	$256.50
Purchase #4	$30.71	7.776%	$33.098	$33.10	$33.10	$33.10
Purchase #5	$37.42	12.186%	$41.98	$41.98	$42.00	$42.00
Purchase #6	$215.25	5.578%	$227.2566	$227.26	$227.25	$227.30
Purchase #7	$177.75	5.491%	$187.5103	$187.51	$187.50	$187.50
7 purchase totals =	$948.95		$1,036.2347	$1,036.24	$1,036.20	$1,036.30