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	$52.45	13.554%	$59.5591	$59.56	$59.55	$59.60
Purchase #2	$113.32	4.244%	$118.1293	$118.13	$118.15	$118.10
Purchase #3	$217.63	13.716%	$247.4801	$247.48	$247.50	$247.50
Purchase #4	$247.85	8.682%	$269.3683	$269.37	$269.35	$269.40
Purchase #5	$136.77	7.853%	$147.5105	$147.51	$147.50	$147.50
Purchase #6	$147.42	7.528%	$158.5178	$158.52	$158.50	$158.50
Purchase #7	$181.36	10.768%	$200.8888	$200.89	$200.90	$200.90
7 purchase totals =	$1,096.80		$1,201.4539	$1,201.46	$1,201.45	$1,201.50