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	$121.58	8.562%	$131.9897	$131.99	$132.00	$132.00
Purchase #2	$16.67	13.487%	$18.9183	$18.92	$18.90	$18.90
Purchase #3	$171.59	11.462%	$191.2576	$191.26	$191.25	$191.30
Purchase #4	$168.66	4.673%	$176.5415	$176.54	$176.55	$176.50
Purchase #5	$35.85	12.512%	$40.3356	$40.34	$40.35	$40.30
Purchase #6	$101.76	3.225%	$105.0418	$105.04	$105.05	$105.00
Purchase #7	$242.59	8.214%	$262.5163	$262.52	$262.50	$262.50
7 purchase totals =	$858.70		$926.6008	$926.61	$926.60	$926.50