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	$199.44	12.517%	$224.4039	$224.40	$224.40	$224.40
Purchase #2	$79.79	4.775%	$83.6	$83.60	$83.60	$83.60
Purchase #3	$177.64	10.436%	$196.1785	$196.18	$196.20	$196.20
Purchase #4	$94.97	11.257%	$105.6608	$105.66	$105.65	$105.70
Purchase #5	$135.44	11.703%	$151.2905	$151.29	$151.30	$151.30
Purchase #6	$136.87	11.800%	$153.0207	$153.02	$153.00	$153.00
Purchase #7	$123.33	11.265%	$137.2231	$137.22	$137.20	$137.20
7 purchase totals =	$947.48		$1,051.3775	$1,051.37	$1,051.35	$1,051.40