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	$235.98	8.707%	$256.5268	$256.53	$256.55	$256.50
Purchase #2	$204.98	7.520%	$220.3945	$220.39	$220.40	$220.40
Purchase #3	$101.63	9.734%	$111.5227	$111.52	$111.50	$111.50
Purchase #4	$135.64	7.531%	$145.855	$145.86	$145.85	$145.90
Purchase #5	$147.66	12.742%	$166.4748	$166.47	$166.45	$166.50
Purchase #6	$209.87	12.772%	$236.6746	$236.67	$236.65	$236.70
Purchase #7	$116.52	11.584%	$130.0177	$130.02	$130.00	$130.00
7 purchase totals =	$1,152.28		$1,267.4661	$1,267.46	$1,267.40	$1,267.50