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	$225.27	13.200%	$255.0056	$255.01	$255.00	$255.00
Purchase #2	$25.44	11.836%	$28.4511	$28.45	$28.45	$28.50
Purchase #3	$242.45	9.362%	$265.1482	$265.15	$265.15	$265.10
Purchase #4	$77.38	10.752%	$85.6999	$85.70	$85.70	$85.70
Purchase #5	$10.52	12.229%	$11.8065	$11.81	$11.80	$11.80
Purchase #6	$216.85	5.113%	$227.9375	$227.94	$227.95	$227.90
Purchase #7	$156.82	8.751%	$170.5433	$170.54	$170.55	$170.50
7 purchase totals =	$954.73		$1,044.5921	$1,044.60	$1,044.60	$1,044.50