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	$157.32	7.302%	$168.8075	$168.81	$168.80	$168.80
Purchase #2	$11.33	10.380%	$12.5061	$12.51	$12.50	$12.50
Purchase #3	$83.31	11.442%	$92.8423	$92.84	$92.85	$92.80
Purchase #4	$242.46	13.320%	$274.7557	$274.76	$274.75	$274.80
Purchase #5	$25.39	9.312%	$27.7543	$27.75	$27.75	$27.80
Purchase #6	$108.29	11.199%	$120.4174	$120.42	$120.40	$120.40
Purchase #7	$159.31	12.682%	$179.5137	$179.51	$179.50	$179.50
7 purchase totals =	$787.41		$876.5970	$876.60	$876.55	$876.60