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	$161.27	4.221%	$168.0772	$168.08	$168.10	$168.10
Purchase #2	$146.86	4.113%	$152.9004	$152.90	$152.90	$152.90
Purchase #3	$249.38	9.818%	$273.8641	$273.86	$273.85	$273.90
Purchase #4	$17.80	11.691%	$19.881	$19.88	$19.90	$19.90
Purchase #5	$41.49	7.868%	$44.7544	$44.75	$44.75	$44.80
Purchase #6	$208.86	13.487%	$237.0289	$237.03	$237.05	$237.00
Purchase #7	$223.64	4.861%	$234.5111	$234.51	$234.50	$234.50
7 purchase totals =	$1,049.30		$1,131.0171	$1,131.01	$1,131.05	$1,131.10