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	$50.26	7.103%	$53.83	$53.83	$53.85	$53.80
Purchase #2	$108.81	8.461%	$118.0164	$118.02	$118.00	$118.00
Purchase #3	$78.54	10.639%	$86.8959	$86.90	$86.90	$86.90
Purchase #4	$40.63	10.842%	$45.0351	$45.04	$45.05	$45.00
Purchase #5	$196.50	10.819%	$217.7593	$217.76	$217.75	$217.80
Purchase #6	$138.66	6.334%	$147.4427	$147.44	$147.45	$147.40
Purchase #7	$215.51	3.583%	$223.2317	$223.23	$223.25	$223.20
7 purchase totals =	$828.91		$892.2111	$892.22	$892.25	$892.10