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	$83.82	12.661%	$94.4325	$94.43	$94.45	$94.40
Purchase #2	$233.27	9.539%	$255.5216	$255.52	$255.50	$255.50
Purchase #3	$97.43	10.469%	$107.6299	$107.63	$107.65	$107.60
Purchase #4	$160.66	12.428%	$180.6268	$180.63	$180.65	$180.60
Purchase #5	$56.30	5.867%	$59.6031	$59.60	$59.60	$59.60
Purchase #6	$247.59	10.847%	$274.4461	$274.45	$274.45	$274.40
Purchase #7	$13.38	7.203%	$14.3438	$14.34	$14.35	$14.30
7 purchase totals =	$892.45		$986.6038	$986.60	$986.65	$986.40