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	$126.59	11.667%	$141.3593	$141.36	$141.35	$141.40
Purchase #2	$57.44	4.236%	$59.8732	$59.87	$59.85	$59.90
Purchase #3	$36.36	5.827%	$38.4787	$38.48	$38.50	$38.50
Purchase #4	$141.61	6.334%	$150.5796	$150.58	$150.60	$150.60
Purchase #5	$166.91	11.833%	$186.6605	$186.66	$186.65	$186.70
Purchase #6	$143.34	13.356%	$162.4845	$162.48	$162.50	$162.50
Purchase #7	$11.57	13.414%	$13.122	$13.12	$13.10	$13.10
7 purchase totals =	$683.82		$752.5578	$752.55	$752.55	$752.70