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	$92.64	11.782%	$103.5548	$103.55	$103.55	$103.60
Purchase #2	$150.53	13.534%	$170.9027	$170.90	$170.90	$170.90
Purchase #3	$110.63	10.476%	$122.2196	$122.22	$122.20	$122.20
Purchase #4	$42.52	5.510%	$44.8629	$44.86	$44.85	$44.90
Purchase #5	$213.39	10.831%	$236.5023	$236.50	$236.50	$236.50
Purchase #6	$53.50	8.261%	$57.9196	$57.92	$57.90	$57.90
Purchase #7	$70.34	11.732%	$78.5923	$78.59	$78.60	$78.60
7 purchase totals =	$733.55		$814.5542	$814.54	$814.50	$814.60