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	$63.94	3.504%	$66.1805	$66.18	$66.20	$66.20
Purchase #2	$243.34	6.119%	$258.23	$258.23	$258.25	$258.20
Purchase #3	$182.47	7.872%	$196.834	$196.83	$196.85	$196.80
Purchase #4	$212.91	3.699%	$220.7855	$220.79	$220.80	$220.80
Purchase #5	$157.88	4.475%	$164.9451	$164.95	$164.95	$164.90
Purchase #6	$163.29	5.627%	$172.4783	$172.48	$172.50	$172.50
Purchase #7	$83.69	5.448%	$88.2494	$88.25	$88.25	$88.20
7 purchase totals =	$1,107.52		$1,167.7028	$1,167.71	$1,167.80	$1,167.60