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	$132.41	5.339%	$139.4794	$139.48	$139.50	$139.50
Purchase #2	$126.39	8.206%	$136.7616	$136.76	$136.75	$136.80
Purchase #3	$138.66	10.238%	$152.856	$152.86	$152.85	$152.90
Purchase #4	$200.85	3.562%	$208.0043	$208.00	$208.00	$208.00
Purchase #5	$79.37	12.266%	$89.1055	$89.11	$89.10	$89.10
Purchase #6	$55.94	5.339%	$58.9266	$58.93	$58.95	$58.90
Purchase #7	$212.87	7.750%	$229.3674	$229.37	$229.35	$229.40
7 purchase totals =	$946.49		$1,014.5008	$1,014.51	$1,014.50	$1,014.60