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	$243.61	10.769%	$269.8444	$269.84	$269.85	$269.80
Purchase #2	$13.95	9.694%	$15.3023	$15.30	$15.30	$15.30
Purchase #3	$196.78	12.547%	$221.47	$221.47	$221.45	$221.50
Purchase #4	$212.90	9.511%	$233.1489	$233.15	$233.15	$233.10
Purchase #5	$147.47	9.531%	$161.5254	$161.53	$161.55	$161.50
Purchase #6	$83.80	7.439%	$90.0339	$90.03	$90.05	$90.00
Purchase #7	$147.65	7.737%	$159.0737	$159.07	$159.05	$159.10
7 purchase totals =	$1,046.16		$1,150.3986	$1,150.39	$1,150.40	$1,150.30