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	$131.41	9.316%	$143.6522	$143.65	$143.65	$143.70
Purchase #2	$33.53	7.829%	$36.1551	$36.16	$36.15	$36.20
Purchase #3	$53.78	13.514%	$61.0478	$61.05	$61.05	$61.00
Purchase #4	$164.54	9.323%	$179.8801	$179.88	$179.90	$179.90
Purchase #5	$191.60	12.203%	$214.9809	$214.98	$215.00	$215.00
Purchase #6	$210.74	3.240%	$217.568	$217.57	$217.55	$217.60
Purchase #7	$205.67	8.699%	$223.5612	$223.56	$223.55	$223.60
7 purchase totals =	$991.27		$1,076.8453	$1,076.85	$1,076.85	$1,077.00