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	$180.97	11.518%	$201.8141	$201.81	$201.80	$201.80
Purchase #2	$124.78	13.420%	$141.5255	$141.53	$141.55	$141.50
Purchase #3	$127.66	3.667%	$132.3413	$132.34	$132.35	$132.30
Purchase #4	$34.27	8.646%	$37.233	$37.23	$37.25	$37.20
Purchase #5	$185.59	7.329%	$199.1919	$199.19	$199.20	$199.20
Purchase #6	$143.67	10.143%	$158.2424	$158.24	$158.25	$158.20
Purchase #7	$214.84	3.535%	$222.4346	$222.43	$222.45	$222.40
7 purchase totals =	$1,011.78		$1,092.7828	$1,092.77	$1,092.85	$1,092.60