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	$144.89	8.364%	$157.0086	$157.01	$157.00	$157.00
Purchase #2	$43.94	3.755%	$45.5899	$45.59	$45.60	$45.60
Purchase #3	$104.50	4.326%	$109.0207	$109.02	$109.00	$109.00
Purchase #4	$145.78	11.304%	$162.259	$162.26	$162.25	$162.30
Purchase #5	$98.41	5.679%	$103.9987	$104.00	$104.00	$104.00
Purchase #6	$108.77	3.870%	$112.9794	$112.98	$113.00	$113.00
Purchase #7	$160.63	6.854%	$171.6396	$171.64	$171.65	$171.60
7 purchase totals =	$806.92		$862.4959	$862.50	$862.50	$862.50