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	$148.84	10.267%	$164.1214	$164.12	$164.10	$164.10
Purchase #2	$66.47	9.664%	$72.8937	$72.89	$72.90	$72.90
Purchase #3	$99.31	12.159%	$111.3851	$111.39	$111.40	$111.40
Purchase #4	$29.89	6.193%	$31.7411	$31.74	$31.75	$31.70
Purchase #5	$14.46	10.604%	$15.9933	$15.99	$16.00	$16.00
Purchase #6	$34.74	12.165%	$38.9661	$38.97	$38.95	$39.00
Purchase #7	$136.82	6.675%	$145.9527	$145.95	$145.95	$146.00
7 purchase totals =	$530.53		$581.0534	$581.05	$581.05	$581.10