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	$237.41	11.313%	$264.2682	$264.27	$264.25	$264.30
Purchase #2	$42.94	13.713%	$48.8284	$48.83	$48.85	$48.80
Purchase #3	$179.48	9.540%	$196.6024	$196.60	$196.60	$196.60
Purchase #4	$217.37	11.181%	$241.6741	$241.67	$241.65	$241.70
Purchase #5	$195.41	10.870%	$216.6511	$216.65	$216.65	$216.70
Purchase #6	$141.69	9.252%	$154.7992	$154.80	$154.80	$154.80
Purchase #7	$48.59	10.536%	$53.7094	$53.71	$53.70	$53.70
7 purchase totals =	$1,062.89		$1,176.5328	$1,176.53	$1,176.50	$1,176.60