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	$96.58	8.538%	$104.826	$104.83	$104.85	$104.80
Purchase #2	$33.48	9.186%	$36.5555	$36.56	$36.55	$36.60
Purchase #3	$35.80	10.662%	$39.617	$39.62	$39.60	$39.60
Purchase #4	$237.40	8.192%	$256.8478	$256.85	$256.85	$256.80
Purchase #5	$85.67	5.180%	$90.1077	$90.11	$90.10	$90.10
Purchase #6	$76.88	13.137%	$86.9797	$86.98	$87.00	$87.00
Purchase #7	$201.53	7.120%	$215.8789	$215.88	$215.90	$215.90
7 purchase totals =	$767.34		$830.8126	$830.83	$830.85	$830.80