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	$106.70	8.818%	$116.1088	$116.11	$116.10	$116.10
Purchase #2	$45.49	12.761%	$51.295	$51.30	$51.30	$51.30
Purchase #3	$187.87	4.627%	$196.5627	$196.56	$196.55	$196.60
Purchase #4	$122.93	11.635%	$137.2329	$137.23	$137.25	$137.20
Purchase #5	$123.56	6.285%	$131.3257	$131.33	$131.35	$131.30
Purchase #6	$10.29	6.370%	$10.9455	$10.95	$10.95	$10.90
Purchase #7	$198.48	11.827%	$221.9542	$221.95	$221.95	$222.00
7 purchase totals =	$795.32		$865.4248	$865.43	$865.45	$865.40