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	$129.42	5.490%	$136.5252	$136.53	$136.55	$136.50
Purchase #2	$116.25	6.322%	$123.5993	$123.60	$123.60	$123.60
Purchase #3	$80.58	7.102%	$86.3028	$86.30	$86.30	$86.30
Purchase #4	$227.55	8.180%	$246.1636	$246.16	$246.15	$246.20
Purchase #5	$225.93	10.839%	$250.4186	$250.42	$250.40	$250.40
Purchase #6	$169.93	8.463%	$184.3112	$184.31	$184.30	$184.30
Purchase #7	$30.94	10.575%	$34.2119	$34.21	$34.20	$34.20
7 purchase totals =	$980.60		$1,061.5326	$1,061.53	$1,061.50	$1,061.50