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	$178.55	11.807%	$199.6314	$199.63	$199.65	$199.60
Purchase #2	$215.72	10.224%	$237.7752	$237.78	$237.80	$237.80
Purchase #3	$92.95	11.277%	$103.432	$103.43	$103.45	$103.40
Purchase #4	$82.95	5.429%	$87.4534	$87.45	$87.45	$87.50
Purchase #5	$201.39	7.589%	$216.6735	$216.67	$216.65	$216.70
Purchase #6	$229.91	13.830%	$261.7066	$261.71	$261.70	$261.70
Purchase #7	$85.90	9.621%	$94.1644	$94.16	$94.15	$94.20
7 purchase totals =	$1,087.37		$1,200.8365	$1,200.83	$1,200.85	$1,200.90