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	$10.31	11.309%	$11.476	$11.48	$11.50	$11.50
Purchase #2	$34.58	6.605%	$36.864	$36.86	$36.85	$36.90
Purchase #3	$54.57	9.828%	$59.9331	$59.93	$59.95	$59.90
Purchase #4	$68.75	7.484%	$73.8953	$73.90	$73.90	$73.90
Purchase #5	$36.50	11.559%	$40.719	$40.72	$40.70	$40.70
Purchase #6	$83.27	3.714%	$86.3626	$86.36	$86.35	$86.40
Purchase #7	$37.67	13.811%	$42.8726	$42.87	$42.85	$42.90
7 purchase totals =	$325.65		$352.1226	$352.12	$352.10	$352.20