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	$109.97	12.640%	$123.8702	$123.87	$123.85	$123.90
Purchase #2	$5.33	10.591%	$5.8945	$5.89	$5.90	$5.90
Purchase #3	$85.53	5.724%	$90.4257	$90.43	$90.45	$90.40
Purchase #4	$109.91	5.659%	$116.1298	$116.13	$116.15	$116.10
Purchase #5	$238.63	13.818%	$271.6039	$271.60	$271.60	$271.60
Purchase #6	$14.59	4.826%	$15.2941	$15.29	$15.30	$15.30
Purchase #7	$244.48	11.490%	$272.5708	$272.57	$272.55	$272.60
7 purchase totals =	$808.44		$895.7890	$895.78	$895.80	$895.80