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	$70.38	3.622%	$72.9292	$72.93	$72.95	$72.90
Purchase #2	$35.95	4.379%	$37.5243	$37.52	$37.50	$37.50
Purchase #3	$81.97	4.393%	$85.5709	$85.57	$85.55	$85.60
Purchase #4	$228.78	7.711%	$246.4212	$246.42	$246.40	$246.40
Purchase #5	$214.31	8.215%	$231.9156	$231.92	$231.90	$231.90
Purchase #6	$10.89	5.328%	$11.4702	$11.47	$11.45	$11.50
Purchase #7	$193.66	12.418%	$217.7087	$217.71	$217.70	$217.70
7 purchase totals =	$835.94		$903.5401	$903.54	$903.45	$903.50