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	$177.33	10.266%	$195.5347	$195.53	$195.55	$195.50
Purchase #2	$246.57	4.762%	$258.3117	$258.31	$258.30	$258.30
Purchase #3	$195.54	10.532%	$216.1343	$216.13	$216.15	$216.10
Purchase #4	$227.56	11.507%	$253.7453	$253.75	$253.75	$253.70
Purchase #5	$64.60	12.321%	$72.5594	$72.56	$72.55	$72.60
Purchase #6	$242.68	4.490%	$253.5763	$253.58	$253.60	$253.60
Purchase #7	$90.93	5.390%	$95.8311	$95.83	$95.85	$95.80
7 purchase totals =	$1,245.21		$1,345.6928	$1,345.69	$1,345.75	$1,345.60