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	$140.32	9.368%	$153.4652	$153.47	$153.45	$153.50
Purchase #2	$17.32	8.162%	$18.7337	$18.73	$18.75	$18.70
Purchase #3	$42.71	6.243%	$45.3764	$45.38	$45.40	$45.40
Purchase #4	$208.92	9.154%	$228.0445	$228.04	$228.05	$228.00
Purchase #5	$225.51	7.129%	$241.5866	$241.59	$241.60	$241.60
Purchase #6	$248.78	12.346%	$279.4944	$279.49	$279.50	$279.50
Purchase #7	$246.72	5.336%	$259.885	$259.89	$259.90	$259.90
7 purchase totals =	$1,130.28		$1,226.5858	$1,226.59	$1,226.65	$1,226.60