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	$123.35	5.657%	$130.3279	$130.33	$130.35	$130.30
Purchase #2	$119.44	10.741%	$132.2691	$132.27	$132.25	$132.30
Purchase #3	$170.85	3.159%	$176.2472	$176.25	$176.25	$176.20
Purchase #4	$87.53	3.255%	$90.3791	$90.38	$90.40	$90.40
Purchase #5	$38.59	5.122%	$40.5666	$40.57	$40.55	$40.60
Purchase #6	$148.45	11.472%	$165.4802	$165.48	$165.50	$165.50
Purchase #7	$17.38	5.712%	$18.3727	$18.37	$18.35	$18.40
7 purchase totals =	$705.59		$753.6428	$753.65	$753.65	$753.70