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	$190.70	7.762%	$205.5021	$205.50	$205.50	$205.50
Purchase #2	$29.85	5.242%	$31.4147	$31.41	$31.40	$31.40
Purchase #3	$26.28	3.236%	$27.1304	$27.13	$27.15	$27.10
Purchase #4	$16.35	7.575%	$17.5885	$17.59	$17.60	$17.60
Purchase #5	$212.41	4.634%	$222.2531	$222.25	$222.25	$222.30
Purchase #6	$26.32	9.674%	$28.8662	$28.87	$28.85	$28.90
Purchase #7	$18.72	11.610%	$20.8934	$20.89	$20.90	$20.90
7 purchase totals =	$520.63		$553.6484	$553.64	$553.65	$553.70