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	$140.61	8.362%	$152.3678	$152.37	$152.35	$152.40
Purchase #2	$75.41	13.676%	$85.7231	$85.72	$85.70	$85.70
Purchase #3	$62.36	9.293%	$68.1551	$68.16	$68.15	$68.20
Purchase #4	$11.38	3.245%	$11.7493	$11.75	$11.75	$11.70
Purchase #5	$163.66	9.694%	$179.5252	$179.53	$179.55	$179.50
Purchase #6	$32.42	7.605%	$34.8855	$34.89	$34.90	$34.90
Purchase #7	$87.93	13.627%	$99.9122	$99.91	$99.90	$99.90
7 purchase totals =	$573.77		$632.3182	$632.33	$632.30	$632.30