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	$12.84	3.803%	$13.3283	$13.33	$13.35	$13.30
Purchase #2	$242.39	5.447%	$255.593	$255.59	$255.60	$255.60
Purchase #3	$93.34	11.284%	$103.8725	$103.87	$103.85	$103.90
Purchase #4	$231.70	6.688%	$247.1961	$247.20	$247.20	$247.20
Purchase #5	$154.96	11.160%	$172.2535	$172.25	$172.25	$172.30
Purchase #6	$27.65	10.290%	$30.4952	$30.50	$30.50	$30.50
Purchase #7	$114.37	8.215%	$123.7655	$123.77	$123.75	$123.80
7 purchase totals =	$877.25		$946.5041	$946.51	$946.50	$946.60