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	$117.57	13.587%	$133.5442	$133.54	$133.55	$133.50
Purchase #2	$144.61	12.343%	$162.4592	$162.46	$162.45	$162.50
Purchase #3	$124.75	3.676%	$129.3358	$129.34	$129.35	$129.30
Purchase #4	$241.61	10.207%	$266.2711	$266.27	$266.25	$266.30
Purchase #5	$164.89	3.761%	$171.0915	$171.09	$171.10	$171.10
Purchase #6	$76.30	3.249%	$78.779	$78.78	$78.80	$78.80
Purchase #7	$75.98	8.407%	$82.3676	$82.37	$82.35	$82.40
7 purchase totals =	$945.71		$1,023.8484	$1,023.85	$1,023.85	$1,023.90