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	$118.54	4.257%	$123.5862	$123.59	$123.60	$123.60
Purchase #2	$28.66	13.316%	$32.4764	$32.48	$32.50	$32.50
Purchase #3	$95.65	6.520%	$101.8864	$101.89	$101.90	$101.90
Purchase #4	$47.96	4.119%	$49.9355	$49.94	$49.95	$49.90
Purchase #5	$137.53	6.772%	$146.8435	$146.84	$146.85	$146.80
Purchase #6	$63.91	5.724%	$67.5682	$67.57	$67.55	$67.60
Purchase #7	$207.60	8.200%	$224.6232	$224.62	$224.60	$224.60
7 purchase totals =	$699.85		$746.9194	$746.93	$746.95	$746.90