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	$179.27	10.531%	$198.1489	$198.15	$198.15	$198.10
Purchase #2	$81.52	6.548%	$86.8579	$86.86	$86.85	$86.90
Purchase #3	$227.37	7.688%	$244.8502	$244.85	$244.85	$244.90
Purchase #4	$66.68	8.405%	$72.2845	$72.28	$72.30	$72.30
Purchase #5	$50.87	11.561%	$56.7511	$56.75	$56.75	$56.80
Purchase #6	$6.52	13.198%	$7.3805	$7.38	$7.40	$7.40
Purchase #7	$105.30	11.306%	$117.2052	$117.21	$117.20	$117.20
7 purchase totals =	$717.53		$783.4783	$783.48	$783.50	$783.60