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	$33.26	12.311%	$37.3546	$37.35	$37.35	$37.40
Purchase #2	$178.76	9.172%	$195.1559	$195.16	$195.15	$195.20
Purchase #3	$135.96	6.799%	$145.2039	$145.20	$145.20	$145.20
Purchase #4	$95.73	7.140%	$102.5651	$102.57	$102.55	$102.60
Purchase #5	$228.51	12.433%	$256.9206	$256.92	$256.90	$256.90
Purchase #6	$103.38	10.772%	$114.5161	$114.52	$114.50	$114.50
Purchase #7	$138.94	4.226%	$144.8116	$144.81	$144.80	$144.80
7 purchase totals =	$914.54		$996.5278	$996.53	$996.45	$996.60