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	$32.50	7.365%	$34.8936	$34.89	$34.90	$34.90
Purchase #2	$137.81	9.833%	$151.3609	$151.36	$151.35	$151.40
Purchase #3	$84.73	3.799%	$87.9489	$87.95	$87.95	$87.90
Purchase #4	$222.30	4.312%	$231.8856	$231.89	$231.90	$231.90
Purchase #5	$192.44	12.714%	$216.9068	$216.91	$216.90	$216.90
Purchase #6	$234.70	5.846%	$248.4206	$248.42	$248.40	$248.40
Purchase #7	$54.69	8.159%	$59.1522	$59.15	$59.15	$59.20
7 purchase totals =	$959.17		$1,030.5686	$1,030.57	$1,030.55	$1,030.60