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	$181.34	6.351%	$192.8569	$192.86	$192.85	$192.90
Purchase #2	$109.32	7.855%	$117.9071	$117.91	$117.90	$117.90
Purchase #3	$155.42	7.358%	$166.8558	$166.86	$166.85	$166.90
Purchase #4	$18.63	6.660%	$19.8708	$19.87	$19.85	$19.90
Purchase #5	$45.94	3.500%	$47.5479	$47.55	$47.55	$47.50
Purchase #6	$191.72	4.448%	$200.2477	$200.25	$200.25	$200.20
Purchase #7	$131.66	13.870%	$149.9212	$149.92	$149.90	$149.90
7 purchase totals =	$834.03		$895.2074	$895.22	$895.15	$895.20