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	$61.61	12.569%	$69.3538	$69.35	$69.35	$69.40
Purchase #2	$185.38	12.571%	$208.6841	$208.68	$208.70	$208.70
Purchase #3	$95.71	3.388%	$98.9527	$98.95	$98.95	$99.00
Purchase #4	$104.28	8.433%	$113.0739	$113.07	$113.05	$113.10
Purchase #5	$71.88	9.233%	$78.5167	$78.52	$78.50	$78.50
Purchase #6	$128.28	6.282%	$136.3385	$136.34	$136.35	$136.30
Purchase #7	$139.59	12.102%	$156.4832	$156.48	$156.50	$156.50
7 purchase totals =	$786.73		$861.4029	$861.39	$861.40	$861.50