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	$151.93	13.557%	$172.5272	$172.53	$172.55	$172.50
Purchase #2	$132.97	10.496%	$146.9265	$146.93	$146.95	$146.90
Purchase #3	$65.64	12.525%	$73.8614	$73.86	$73.85	$73.90
Purchase #4	$211.98	5.135%	$222.8652	$222.87	$222.85	$222.90
Purchase #5	$249.99	12.571%	$281.4162	$281.42	$281.40	$281.40
Purchase #6	$67.64	7.718%	$72.8605	$72.86	$72.85	$72.90
Purchase #7	$118.82	5.593%	$125.4656	$125.47	$125.45	$125.50
7 purchase totals =	$998.97		$1,095.9226	$1,095.94	$1,095.90	$1,096.00