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	$85.60	10.443%	$94.5392	$94.54	$94.55	$94.50
Purchase #2	$163.27	5.430%	$172.1356	$172.14	$172.15	$172.10
Purchase #3	$168.71	12.773%	$190.2593	$190.26	$190.25	$190.30
Purchase #4	$14.60	4.506%	$15.2579	$15.26	$15.25	$15.30
Purchase #5	$150.96	12.797%	$170.2784	$170.28	$170.30	$170.30
Purchase #6	$88.34	10.130%	$97.2888	$97.29	$97.30	$97.30
Purchase #7	$73.39	6.294%	$78.0092	$78.01	$78.00	$78.00
7 purchase totals =	$744.87		$817.7684	$817.78	$817.80	$817.80