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	$86.54	6.850%	$92.468	$92.47	$92.45	$92.50
Purchase #2	$31.46	10.667%	$34.8158	$34.82	$34.80	$34.80
Purchase #3	$81.83	9.189%	$89.3494	$89.35	$89.35	$89.30
Purchase #4	$216.57	3.254%	$223.6172	$223.62	$223.60	$223.60
Purchase #5	$159.76	5.178%	$168.0324	$168.03	$168.05	$168.00
Purchase #6	$156.26	10.417%	$172.5376	$172.54	$172.55	$172.50
Purchase #7	$178.66	7.844%	$192.6741	$192.67	$192.65	$192.70
7 purchase totals =	$911.08		$973.4945	$973.50	$973.45	$973.40