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	$186.71	10.232%	$205.8142	$205.81	$205.80	$205.80
Purchase #2	$100.60	3.320%	$103.9399	$103.94	$103.95	$103.90
Purchase #3	$168.84	8.157%	$182.6123	$182.61	$182.60	$182.60
Purchase #4	$43.28	5.180%	$45.5219	$45.52	$45.50	$45.50
Purchase #5	$120.84	11.628%	$134.8913	$134.89	$134.90	$134.90
Purchase #6	$221.27	4.800%	$231.891	$231.89	$231.90	$231.90
Purchase #7	$45.57	5.562%	$48.1046	$48.10	$48.10	$48.10
7 purchase totals =	$887.11		$952.7752	$952.76	$952.75	$952.70