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	$225.50	9.582%	$247.1074	$247.11	$247.10	$247.10
Purchase #2	$211.66	3.337%	$218.7231	$218.72	$218.70	$218.70
Purchase #3	$116.39	13.371%	$131.9525	$131.95	$131.95	$132.00
Purchase #4	$37.74	8.463%	$40.9339	$40.93	$40.95	$40.90
Purchase #5	$206.87	7.628%	$222.65	$222.65	$222.65	$222.70
Purchase #6	$134.75	13.475%	$152.9076	$152.91	$152.90	$152.90
Purchase #7	$25.93	8.690%	$28.1833	$28.18	$28.20	$28.20
7 purchase totals =	$958.84		$1,042.4578	$1,042.45	$1,042.45	$1,042.50