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	$134.96	12.807%	$152.2443	$152.24	$152.25	$152.20
Purchase #2	$108.83	13.333%	$123.3403	$123.34	$123.35	$123.30
Purchase #3	$94.77	3.442%	$98.032	$98.03	$98.05	$98.00
Purchase #4	$212.68	11.418%	$236.9638	$236.96	$236.95	$237.00
Purchase #5	$32.54	3.551%	$33.6955	$33.70	$33.70	$33.70
Purchase #6	$187.83	4.548%	$196.3725	$196.37	$196.35	$196.40
Purchase #7	$40.80	9.337%	$44.6095	$44.61	$44.60	$44.60
7 purchase totals =	$812.41		$885.2579	$885.25	$885.25	$885.20