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	$109.38	13.781%	$124.4537	$124.45	$124.45	$124.50
Purchase #2	$57.29	4.634%	$59.9448	$59.94	$59.95	$59.90
Purchase #3	$243.99	12.706%	$274.9914	$274.99	$275.00	$275.00
Purchase #4	$44.26	10.828%	$49.0525	$49.05	$49.05	$49.10
Purchase #5	$60.91	11.510%	$67.9207	$67.92	$67.90	$67.90
Purchase #6	$93.27	7.734%	$100.4835	$100.48	$100.50	$100.50
Purchase #7	$199.48	4.743%	$208.9413	$208.94	$208.95	$208.90
7 purchase totals =	$808.58		$885.7879	$885.77	$885.80	$885.80