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	$225.73	3.437%	$233.4883	$233.49	$233.50	$233.50
Purchase #2	$239.95	8.240%	$259.7219	$259.72	$259.70	$259.70
Purchase #3	$125.94	12.412%	$141.5717	$141.57	$141.55	$141.60
Purchase #4	$133.43	9.762%	$146.4554	$146.46	$146.45	$146.50
Purchase #5	$28.32	11.320%	$31.5258	$31.53	$31.55	$31.50
Purchase #6	$24.35	11.226%	$27.0835	$27.08	$27.10	$27.10
Purchase #7	$97.56	3.197%	$100.679	$100.68	$100.70	$100.70
7 purchase totals =	$875.28		$940.5256	$940.53	$940.55	$940.60