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	$214.30	3.202%	$221.1619	$221.16	$221.15	$221.20
Purchase #2	$146.66	12.408%	$164.8576	$164.86	$164.85	$164.90
Purchase #3	$48.88	11.492%	$54.4973	$54.50	$54.50	$54.50
Purchase #4	$163.54	12.651%	$184.2294	$184.23	$184.25	$184.20
Purchase #5	$175.49	11.658%	$195.9486	$195.95	$195.95	$195.90
Purchase #6	$164.84	8.624%	$179.0558	$179.06	$179.05	$179.10
Purchase #7	$37.63	8.122%	$40.6863	$40.69	$40.70	$40.70
7 purchase totals =	$951.34		$1,040.4369	$1,040.45	$1,040.45	$1,040.50