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	$131.42	10.245%	$144.884	$144.88	$144.90	$144.90
Purchase #2	$10.32	4.241%	$10.7577	$10.76	$10.75	$10.80
Purchase #3	$69.89	9.616%	$76.6106	$76.61	$76.60	$76.60
Purchase #4	$65.77	10.863%	$72.9146	$72.91	$72.90	$72.90
Purchase #5	$226.55	13.264%	$256.5996	$256.60	$256.60	$256.60
Purchase #6	$63.75	8.575%	$69.2166	$69.22	$69.20	$69.20
Purchase #7	$78.95	4.867%	$82.7925	$82.79	$82.80	$82.80
7 purchase totals =	$646.65		$713.7756	$713.77	$713.75	$713.80