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	$18.34	12.803%	$20.6881	$20.69	$20.70	$20.70
Purchase #2	$155.65	10.460%	$171.931	$171.93	$171.95	$171.90
Purchase #3	$245.94	4.437%	$256.8524	$256.85	$256.85	$256.90
Purchase #4	$68.40	11.634%	$76.3577	$76.36	$76.35	$76.40
Purchase #5	$57.79	3.314%	$59.7052	$59.71	$59.70	$59.70
Purchase #6	$75.98	12.362%	$85.3726	$85.37	$85.35	$85.40
Purchase #7	$60.26	6.359%	$64.0919	$64.09	$64.10	$64.10
7 purchase totals =	$682.36		$734.9989	$735.00	$735.00	$735.10