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	$147.67	3.569%	$152.9403	$152.94	$152.95	$152.90
Purchase #2	$137.95	13.366%	$156.3884	$156.39	$156.40	$156.40
Purchase #3	$227.42	11.440%	$253.4368	$253.44	$253.45	$253.40
Purchase #4	$97.89	13.651%	$111.253	$111.25	$111.25	$111.30
Purchase #5	$231.87	11.579%	$258.7182	$258.72	$258.70	$258.70
Purchase #6	$230.26	11.547%	$256.8481	$256.85	$256.85	$256.80
Purchase #7	$174.41	10.547%	$192.805	$192.81	$192.80	$192.80
7 purchase totals =	$1,247.47		$1,382.3898	$1,382.40	$1,382.40	$1,382.30