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	$107.61	8.238%	$116.4749	$116.47	$116.45	$116.50
Purchase #2	$35.96	5.474%	$37.9285	$37.93	$37.95	$37.90
Purchase #3	$45.58	12.590%	$51.3185	$51.32	$51.30	$51.30
Purchase #4	$86.39	7.523%	$92.8891	$92.89	$92.90	$92.90
Purchase #5	$72.28	5.162%	$76.0111	$76.01	$76.00	$76.00
Purchase #6	$113.59	6.722%	$121.2255	$121.23	$121.25	$121.20
Purchase #7	$61.56	6.664%	$65.6624	$65.66	$65.65	$65.70
7 purchase totals =	$522.97		$561.5100	$561.51	$561.50	$561.50