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	$43.33	3.634%	$44.9046	$44.90	$44.90	$44.90
Purchase #2	$152.97	9.796%	$167.9549	$167.95	$167.95	$168.00
Purchase #3	$25.49	7.650%	$27.44	$27.44	$27.45	$27.40
Purchase #4	$62.86	11.131%	$69.8569	$69.86	$69.85	$69.90
Purchase #5	$102.46	11.743%	$114.4919	$114.49	$114.50	$114.50
Purchase #6	$92.37	13.534%	$104.8714	$104.87	$104.85	$104.90
Purchase #7	$29.77	7.177%	$31.9066	$31.91	$31.90	$31.90
7 purchase totals =	$509.25		$561.4263	$561.42	$561.40	$561.50