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	$175.39	8.338%	$190.014	$190.01	$190.00	$190.00
Purchase #2	$97.93	6.581%	$104.3748	$104.37	$104.35	$104.40
Purchase #3	$16.67	10.308%	$18.3883	$18.39	$18.40	$18.40
Purchase #4	$63.32	12.349%	$71.1394	$71.14	$71.15	$71.10
Purchase #5	$113.56	9.466%	$124.3096	$124.31	$124.30	$124.30
Purchase #6	$219.83	10.491%	$242.8924	$242.89	$242.90	$242.90
Purchase #7	$145.29	12.107%	$162.8803	$162.88	$162.90	$162.90
7 purchase totals =	$831.99		$913.9988	$913.99	$914.00	$914.00