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	$210.28	9.307%	$229.8508	$229.85	$229.85	$229.90
Purchase #2	$31.82	11.177%	$35.3765	$35.38	$35.40	$35.40
Purchase #3	$55.27	8.256%	$59.8331	$59.83	$59.85	$59.80
Purchase #4	$71.38	3.684%	$74.0096	$74.01	$74.00	$74.00
Purchase #5	$39.27	9.686%	$43.0737	$43.07	$43.05	$43.10
Purchase #6	$225.81	7.685%	$243.1635	$243.16	$243.15	$243.20
Purchase #7	$150.79	8.749%	$163.9826	$163.98	$164.00	$164.00
7 purchase totals =	$784.62		$849.2898	$849.28	$849.30	$849.40