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	$232.49	6.502%	$247.6065	$247.61	$247.60	$247.60
Purchase #2	$59.95	12.610%	$67.5097	$67.51	$67.50	$67.50
Purchase #3	$136.27	6.354%	$144.9286	$144.93	$144.95	$144.90
Purchase #4	$178.55	11.174%	$198.5012	$198.50	$198.50	$198.50
Purchase #5	$198.63	13.405%	$225.2564	$225.26	$225.25	$225.30
Purchase #6	$111.54	6.384%	$118.6607	$118.66	$118.65	$118.70
Purchase #7	$243.49	7.535%	$261.837	$261.84	$261.85	$261.80
7 purchase totals =	$1,160.92		$1,264.3001	$1,264.31	$1,264.30	$1,264.30