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	$49.40	9.450%	$54.0683	$54.07	$54.05	$54.10
Purchase #2	$85.29	6.268%	$90.636	$90.64	$90.65	$90.60
Purchase #3	$148.76	3.849%	$154.4858	$154.49	$154.50	$154.50
Purchase #4	$144.94	10.264%	$159.8166	$159.82	$159.80	$159.80
Purchase #5	$160.96	7.431%	$172.9209	$172.92	$172.90	$172.90
Purchase #6	$48.89	8.498%	$53.0447	$53.04	$53.05	$53.00
Purchase #7	$217.45	13.839%	$247.5429	$247.54	$247.55	$247.50
7 purchase totals =	$855.69		$932.5152	$932.52	$932.50	$932.40