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	$91.47	10.253%	$100.8484	$100.85	$100.85	$100.80
Purchase #2	$14.88	3.350%	$15.3785	$15.38	$15.40	$15.40
Purchase #3	$142.71	13.496%	$161.9701	$161.97	$161.95	$162.00
Purchase #4	$33.76	10.183%	$37.1978	$37.20	$37.20	$37.20
Purchase #5	$142.59	9.770%	$156.521	$156.52	$156.50	$156.50
Purchase #6	$197.77	3.681%	$205.0499	$205.05	$205.05	$205.00
Purchase #7	$211.73	6.533%	$225.5623	$225.56	$225.55	$225.60
7 purchase totals =	$834.91		$902.5280	$902.53	$902.50	$902.50