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	$132.51	10.509%	$146.4355	$146.44	$146.45	$146.40
Purchase #2	$64.40	13.756%	$73.2589	$73.26	$73.25	$73.30
Purchase #3	$33.90	8.461%	$36.7683	$36.77	$36.75	$36.80
Purchase #4	$131.25	7.288%	$140.8155	$140.82	$140.80	$140.80
Purchase #5	$32.91	13.862%	$37.472	$37.47	$37.45	$37.50
Purchase #6	$174.51	4.623%	$182.5776	$182.58	$182.60	$182.60
Purchase #7	$153.45	9.691%	$168.3208	$168.32	$168.30	$168.30
7 purchase totals =	$722.93		$785.6486	$785.66	$785.60	$785.70