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	$61.42	9.579%	$67.3034	$67.30	$67.30	$67.30
Purchase #2	$17.53	8.350%	$18.9938	$18.99	$19.00	$19.00
Purchase #3	$98.89	10.609%	$109.3812	$109.38	$109.40	$109.40
Purchase #4	$50.43	11.539%	$56.2491	$56.25	$56.25	$56.20
Purchase #5	$92.94	5.373%	$97.9337	$97.93	$97.95	$97.90
Purchase #6	$53.57	3.621%	$55.5098	$55.51	$55.50	$55.50
Purchase #7	$59.34	7.174%	$63.5971	$63.60	$63.60	$63.60
7 purchase totals =	$434.12		$468.9681	$468.96	$469.00	$468.90