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	$68.78	13.359%	$77.9683	$77.97	$77.95	$78.00
Purchase #2	$94.75	4.491%	$99.0052	$99.01	$99.00	$99.00
Purchase #3	$77.79	11.653%	$86.8549	$86.85	$86.85	$86.90
Purchase #4	$113.35	7.774%	$122.1618	$122.16	$122.15	$122.20
Purchase #5	$225.73	13.269%	$255.6821	$255.68	$255.70	$255.70
Purchase #6	$233.49	13.340%	$264.6376	$264.64	$264.65	$264.60
Purchase #7	$108.58	7.400%	$116.6149	$116.61	$116.60	$116.60
7 purchase totals =	$922.47		$1,022.9248	$1,022.92	$1,022.90	$1,023.00