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	$160.80	7.184%	$172.3519	$172.35	$172.35	$172.40
Purchase #2	$184.42	4.424%	$192.5787	$192.58	$192.60	$192.60
Purchase #3	$62.75	4.600%	$65.6365	$65.64	$65.65	$65.60
Purchase #4	$29.42	5.369%	$30.9996	$31.00	$31.00	$31.00
Purchase #5	$105.25	4.455%	$109.9389	$109.94	$109.95	$109.90
Purchase #6	$66.48	9.334%	$72.6852	$72.69	$72.70	$72.70
Purchase #7	$72.92	4.725%	$76.3655	$76.37	$76.35	$76.40
7 purchase totals =	$682.04		$720.5563	$720.57	$720.60	$720.60