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	$82.69	4.638%	$86.5252	$86.53	$86.55	$86.50
Purchase #2	$152.81	10.822%	$169.3471	$169.35	$169.35	$169.30
Purchase #3	$122.50	3.575%	$126.8794	$126.88	$126.90	$126.90
Purchase #4	$146.48	4.413%	$152.9442	$152.94	$152.95	$152.90
Purchase #5	$132.95	3.371%	$137.4317	$137.43	$137.45	$137.40
Purchase #6	$208.31	4.797%	$218.3026	$218.30	$218.30	$218.30
Purchase #7	$162.34	6.711%	$173.2346	$173.23	$173.25	$173.20
7 purchase totals =	$1,008.08		$1,064.6648	$1,064.66	$1,064.75	$1,064.50