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	$247.82	9.184%	$270.5798	$270.58	$270.60	$270.60
Purchase #2	$89.42	7.531%	$96.1542	$96.15	$96.15	$96.20
Purchase #3	$32.75	5.516%	$34.5565	$34.56	$34.55	$34.60
Purchase #4	$159.96	12.464%	$179.8974	$179.90	$179.90	$179.90
Purchase #5	$71.81	9.186%	$78.4065	$78.41	$78.40	$78.40
Purchase #6	$179.39	11.754%	$200.4755	$200.48	$200.50	$200.50
Purchase #7	$101.72	11.165%	$113.077	$113.08	$113.10	$113.10
7 purchase totals =	$882.87		$973.1469	$973.16	$973.20	$973.30