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	$193.48	11.487%	$215.705	$215.71	$215.70	$215.70
Purchase #2	$190.93	9.379%	$208.8373	$208.84	$208.85	$208.80
Purchase #3	$59.95	5.626%	$63.3228	$63.32	$63.30	$63.30
Purchase #4	$99.57	6.347%	$105.8897	$105.89	$105.90	$105.90
Purchase #5	$37.46	9.216%	$40.9123	$40.91	$40.90	$40.90
Purchase #6	$23.70	3.576%	$24.5475	$24.55	$24.55	$24.50
Purchase #7	$72.60	10.609%	$80.3021	$80.30	$80.30	$80.30
7 purchase totals =	$677.69		$739.5167	$739.52	$739.50	$739.40