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	$37.52	7.172%	$40.2109	$40.21	$40.20	$40.20
Purchase #2	$73.40	12.134%	$82.3064	$82.31	$82.30	$82.30
Purchase #3	$151.59	6.662%	$161.6889	$161.69	$161.70	$161.70
Purchase #4	$24.60	3.700%	$25.5102	$25.51	$25.50	$25.50
Purchase #5	$77.89	10.745%	$86.2593	$86.26	$86.25	$86.30
Purchase #6	$127.47	9.429%	$139.4891	$139.49	$139.50	$139.50
Purchase #7	$27.54	5.671%	$29.1018	$29.10	$29.10	$29.10
7 purchase totals =	$520.01		$564.5666	$564.57	$564.55	$564.60