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	$43.76	3.385%	$45.2413	$45.24	$45.25	$45.20
Purchase #2	$204.25	12.563%	$229.9099	$229.91	$229.90	$229.90
Purchase #3	$139.41	8.189%	$150.8263	$150.83	$150.85	$150.80
Purchase #4	$201.51	6.103%	$213.8082	$213.81	$213.80	$213.80
Purchase #5	$117.52	7.189%	$125.9685	$125.97	$125.95	$126.00
Purchase #6	$144.38	13.797%	$164.3001	$164.30	$164.30	$164.30
Purchase #7	$94.68	9.726%	$103.8886	$103.89	$103.90	$103.90
7 purchase totals =	$945.51		$1,033.9429	$1,033.95	$1,033.95	$1,033.90