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	$139.71	8.434%	$151.4931	$151.49	$151.50	$151.50
Purchase #2	$180.79	8.572%	$196.2873	$196.29	$196.30	$196.30
Purchase #3	$136.59	9.772%	$149.9376	$149.94	$149.95	$149.90
Purchase #4	$130.42	4.808%	$136.6906	$136.69	$136.70	$136.70
Purchase #5	$92.59	11.759%	$103.4777	$103.48	$103.50	$103.50
Purchase #6	$107.35	4.545%	$112.2291	$112.23	$112.25	$112.20
Purchase #7	$66.69	10.434%	$73.6484	$73.65	$73.65	$73.60
7 purchase totals =	$854.14		$923.7638	$923.77	$923.85	$923.70