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	$242.49	13.614%	$275.5026	$275.50	$275.50	$275.50
Purchase #2	$64.91	8.587%	$70.4838	$70.48	$70.50	$70.50
Purchase #3	$23.79	6.708%	$25.3858	$25.39	$25.40	$25.40
Purchase #4	$217.41	10.747%	$240.7751	$240.78	$240.80	$240.80
Purchase #5	$242.61	5.691%	$256.4169	$256.42	$256.40	$256.40
Purchase #6	$199.92	13.726%	$227.361	$227.36	$227.35	$227.40
Purchase #7	$151.43	11.258%	$168.478	$168.48	$168.50	$168.50
7 purchase totals =	$1,142.56		$1,264.4032	$1,264.41	$1,264.45	$1,264.50