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	$249.59	10.539%	$275.8943	$275.89	$275.90	$275.90
Purchase #2	$69.25	4.521%	$72.3808	$72.38	$72.40	$72.40
Purchase #3	$99.84	11.523%	$111.3446	$111.34	$111.35	$111.30
Purchase #4	$213.60	6.273%	$226.9991	$227.00	$227.00	$227.00
Purchase #5	$227.39	9.792%	$249.656	$249.66	$249.65	$249.70
Purchase #6	$234.56	13.637%	$266.5469	$266.55	$266.55	$266.50
Purchase #7	$225.49	9.788%	$247.561	$247.56	$247.55	$247.60
7 purchase totals =	$1,319.72		$1,450.3827	$1,450.38	$1,450.40	$1,450.40