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	$42.89	8.423%	$46.5026	$46.50	$46.50	$46.50
Purchase #2	$39.77	8.790%	$43.2658	$43.27	$43.25	$43.30
Purchase #3	$246.66	6.294%	$262.1848	$262.18	$262.20	$262.20
Purchase #4	$105.28	3.410%	$108.87	$108.87	$108.85	$108.90
Purchase #5	$35.81	7.587%	$38.5269	$38.53	$38.55	$38.50
Purchase #6	$75.64	7.824%	$81.5581	$81.56	$81.55	$81.60
Purchase #7	$79.50	9.398%	$86.9714	$86.97	$86.95	$87.00
7 purchase totals =	$625.55		$667.8796	$667.88	$667.85	$668.00