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	$49.70	3.362%	$51.3709	$51.37	$51.35	$51.40
Purchase #2	$214.95	13.288%	$243.5126	$243.51	$243.50	$243.50
Purchase #3	$197.51	11.466%	$220.1565	$220.16	$220.15	$220.20
Purchase #4	$135.57	11.333%	$150.9341	$150.93	$150.95	$150.90
Purchase #5	$118.90	11.738%	$132.8565	$132.86	$132.85	$132.90
Purchase #6	$207.54	6.414%	$220.8516	$220.85	$220.85	$220.90
Purchase #7	$41.40	9.526%	$45.3438	$45.34	$45.35	$45.30
7 purchase totals =	$965.57		$1,065.0260	$1,065.02	$1,065.00	$1,065.10