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	$247.94	13.580%	$281.6103	$281.61	$281.60	$281.60
Purchase #2	$228.79	7.136%	$245.1165	$245.12	$245.10	$245.10
Purchase #3	$37.71	11.513%	$42.0516	$42.05	$42.05	$42.10
Purchase #4	$217.37	7.603%	$233.8966	$233.90	$233.90	$233.90
Purchase #5	$86.73	13.828%	$98.723	$98.72	$98.70	$98.70
Purchase #6	$54.44	5.577%	$57.4761	$57.48	$57.50	$57.50
Purchase #7	$198.65	11.722%	$221.9358	$221.94	$221.95	$221.90
7 purchase totals =	$1,071.63		$1,180.8099	$1,180.82	$1,180.80	$1,180.80