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	$67.74	7.210%	$72.6241	$72.62	$72.60	$72.60
Purchase #2	$176.28	5.487%	$185.9525	$185.95	$185.95	$186.00
Purchase #3	$87.53	3.767%	$90.8273	$90.83	$90.85	$90.80
Purchase #4	$225.45	3.798%	$234.0126	$234.01	$234.00	$234.00
Purchase #5	$222.73	4.363%	$232.4477	$232.45	$232.45	$232.40
Purchase #6	$91.90	11.497%	$102.4657	$102.47	$102.45	$102.50
Purchase #7	$205.38	6.421%	$218.5674	$218.57	$218.55	$218.60
7 purchase totals =	$1,077.01		$1,136.8973	$1,136.90	$1,136.85	$1,136.90