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	$168.77	10.574%	$186.6157	$186.62	$186.60	$186.60
Purchase #2	$199.49	12.705%	$224.8352	$224.84	$224.85	$224.80
Purchase #3	$54.32	3.564%	$56.256	$56.26	$56.25	$56.30
Purchase #4	$164.51	13.217%	$186.2533	$186.25	$186.25	$186.30
Purchase #5	$157.39	8.655%	$171.0121	$171.01	$171.00	$171.00
Purchase #6	$209.93	3.112%	$216.463	$216.46	$216.45	$216.50
Purchase #7	$116.96	5.582%	$123.4887	$123.49	$123.50	$123.50
7 purchase totals =	$1,071.37		$1,164.9240	$1,164.93	$1,164.90	$1,165.00