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	$43.50	3.176%	$44.8816	$44.88	$44.90	$44.90
Purchase #2	$121.34	8.331%	$131.4488	$131.45	$131.45	$131.40
Purchase #3	$182.86	10.409%	$201.8939	$201.89	$201.90	$201.90
Purchase #4	$147.34	7.544%	$158.4553	$158.46	$158.45	$158.50
Purchase #5	$48.25	7.471%	$51.8548	$51.85	$51.85	$51.90
Purchase #6	$218.71	3.186%	$225.6781	$225.68	$225.70	$225.70
Purchase #7	$57.64	6.304%	$61.2736	$61.27	$61.25	$61.30
7 purchase totals =	$819.64		$875.4861	$875.48	$875.50	$875.60