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	$149.47	13.614%	$169.8188	$169.82	$169.80	$169.80
Purchase #2	$132.35	9.475%	$144.8902	$144.89	$144.90	$144.90
Purchase #3	$204.34	4.248%	$213.0204	$213.02	$213.00	$213.00
Purchase #4	$18.96	8.777%	$20.6241	$20.62	$20.60	$20.60
Purchase #5	$162.74	5.662%	$171.9543	$171.95	$171.95	$172.00
Purchase #6	$151.68	4.605%	$158.6649	$158.66	$158.65	$158.70
Purchase #7	$157.88	4.866%	$165.5624	$165.56	$165.55	$165.60
7 purchase totals =	$977.42		$1,044.5351	$1,044.52	$1,044.45	$1,044.60