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	$211.59	6.494%	$225.3307	$225.33	$225.35	$225.30
Purchase #2	$134.38	6.443%	$143.0381	$143.04	$143.05	$143.00
Purchase #3	$230.95	10.510%	$255.2228	$255.22	$255.20	$255.20
Purchase #4	$135.73	11.638%	$151.5263	$151.53	$151.55	$151.50
Purchase #5	$213.65	11.776%	$238.8094	$238.81	$238.80	$238.80
Purchase #6	$204.55	9.798%	$224.5918	$224.59	$224.60	$224.60
Purchase #7	$209.89	10.356%	$231.6262	$231.63	$231.65	$231.60
7 purchase totals =	$1,340.74		$1,470.1453	$1,470.15	$1,470.20	$1,470.00