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	$171.83	13.426%	$194.8999	$194.90	$194.90	$194.90
Purchase #2	$51.77	4.610%	$54.1566	$54.16	$54.15	$54.20
Purchase #3	$111.73	13.642%	$126.9722	$126.97	$126.95	$127.00
Purchase #4	$39.51	6.728%	$42.1682	$42.17	$42.15	$42.20
Purchase #5	$164.25	12.863%	$185.3775	$185.38	$185.40	$185.40
Purchase #6	$161.44	11.769%	$180.4399	$180.44	$180.45	$180.40
Purchase #7	$126.82	12.632%	$142.8399	$142.84	$142.85	$142.80
7 purchase totals =	$827.35		$926.8542	$926.86	$926.85	$926.90