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	$59.46	12.534%	$66.9127	$66.91	$66.90	$66.90
Purchase #2	$213.59	6.297%	$227.0398	$227.04	$227.05	$227.00
Purchase #3	$152.57	13.284%	$172.8374	$172.84	$172.85	$172.80
Purchase #4	$151.53	7.287%	$162.572	$162.57	$162.55	$162.60
Purchase #5	$169.99	6.249%	$180.6127	$180.61	$180.60	$180.60
Purchase #6	$104.76	6.388%	$111.4521	$111.45	$111.45	$111.50
Purchase #7	$233.61	9.573%	$255.9735	$255.97	$255.95	$256.00
7 purchase totals =	$1,085.51		$1,177.4002	$1,177.39	$1,177.35	$1,177.40