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	$182.54	4.271%	$190.3363	$190.34	$190.35	$190.30
Purchase #2	$74.60	10.661%	$82.5531	$82.55	$82.55	$82.60
Purchase #3	$40.32	6.166%	$42.8061	$42.81	$42.80	$42.80
Purchase #4	$173.40	8.143%	$187.52	$187.52	$187.50	$187.50
Purchase #5	$191.67	13.874%	$218.2623	$218.26	$218.25	$218.30
Purchase #6	$85.77	6.161%	$91.0543	$91.05	$91.05	$91.10
Purchase #7	$133.33	6.862%	$142.4791	$142.48	$142.50	$142.50
7 purchase totals =	$881.63		$955.0112	$955.01	$955.00	$955.10