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	$149.52	8.785%	$162.6553	$162.66	$162.65	$162.70
Purchase #2	$37.32	9.103%	$40.7172	$40.72	$40.70	$40.70
Purchase #3	$176.43	3.452%	$182.5204	$182.52	$182.50	$182.50
Purchase #4	$81.66	4.864%	$85.6319	$85.63	$85.65	$85.60
Purchase #5	$125.51	13.850%	$142.8931	$142.89	$142.90	$142.90
Purchase #6	$56.74	4.320%	$59.1912	$59.19	$59.20	$59.20
Purchase #7	$217.47	6.448%	$231.4925	$231.49	$231.50	$231.50
7 purchase totals =	$844.65		$905.1016	$905.10	$905.10	$905.10