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	$227.56	5.625%	$240.3603	$240.36	$240.35	$240.40
Purchase #2	$150.68	11.838%	$168.5175	$168.52	$168.50	$168.50
Purchase #3	$89.38	10.168%	$98.4682	$98.47	$98.45	$98.50
Purchase #4	$60.74	9.587%	$66.5631	$66.56	$66.55	$66.60
Purchase #5	$21.70	12.579%	$24.4296	$24.43	$24.45	$24.40
Purchase #6	$229.81	7.320%	$246.6321	$246.63	$246.65	$246.60
Purchase #7	$174.59	8.593%	$189.5925	$189.59	$189.60	$189.60
7 purchase totals =	$954.46		$1,034.5633	$1,034.56	$1,034.55	$1,034.60