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	$193.91	11.401%	$216.0177	$216.02	$216.00	$216.00
Purchase #2	$189.97	3.668%	$196.9381	$196.94	$196.95	$196.90
Purchase #3	$204.31	6.773%	$218.1479	$218.15	$218.15	$218.10
Purchase #4	$113.73	7.402%	$122.1483	$122.15	$122.15	$122.10
Purchase #5	$178.66	4.249%	$186.2513	$186.25	$186.25	$186.30
Purchase #6	$186.50	11.566%	$208.0706	$208.07	$208.05	$208.10
Purchase #7	$83.30	8.587%	$90.453	$90.45	$90.45	$90.50
7 purchase totals =	$1,150.38		$1,238.0269	$1,238.03	$1,238.00	$1,238.00