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	$126.74	4.136%	$131.982	$131.98	$132.00	$132.00
Purchase #2	$79.28	8.534%	$86.0458	$86.05	$86.05	$86.00
Purchase #3	$80.78	11.526%	$90.0907	$90.09	$90.10	$90.10
Purchase #4	$228.72	13.118%	$258.7235	$258.72	$258.70	$258.70
Purchase #5	$214.86	3.750%	$222.9173	$222.92	$222.90	$222.90
Purchase #6	$56.98	9.261%	$62.2569	$62.26	$62.25	$62.30
Purchase #7	$199.74	11.526%	$222.762	$222.76	$222.75	$222.80
7 purchase totals =	$987.10		$1,074.7782	$1,074.78	$1,074.75	$1,074.80