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	$178.71	3.710%	$185.3401	$185.34	$185.35	$185.30
Purchase #2	$12.77	13.212%	$14.4572	$14.46	$14.45	$14.50
Purchase #3	$232.82	10.301%	$256.8028	$256.80	$256.80	$256.80
Purchase #4	$221.58	13.203%	$250.8352	$250.84	$250.85	$250.80
Purchase #5	$40.56	5.207%	$42.672	$42.67	$42.65	$42.70
Purchase #6	$131.74	6.157%	$139.8512	$139.85	$139.85	$139.90
Purchase #7	$14.65	5.780%	$15.4968	$15.50	$15.50	$15.50
7 purchase totals =	$832.83		$905.4553	$905.46	$905.45	$905.50