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	$171.66	8.119%	$185.5971	$185.60	$185.60	$185.60
Purchase #2	$19.82	8.422%	$21.4892	$21.49	$21.50	$21.50
Purchase #3	$201.87	11.141%	$224.3603	$224.36	$224.35	$224.40
Purchase #4	$131.72	12.220%	$147.8162	$147.82	$147.80	$147.80
Purchase #5	$196.87	13.847%	$224.1306	$224.13	$224.15	$224.10
Purchase #6	$53.79	8.702%	$58.4708	$58.47	$58.45	$58.50
Purchase #7	$126.28	13.638%	$143.5021	$143.50	$143.50	$143.50
7 purchase totals =	$902.01		$1,005.3663	$1,005.37	$1,005.35	$1,005.40