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	$111.88	10.631%	$123.774	$123.77	$123.75	$123.80
Purchase #2	$208.73	6.816%	$222.957	$222.96	$222.95	$223.00
Purchase #3	$41.59	10.465%	$45.9424	$45.94	$45.95	$45.90
Purchase #4	$27.67	8.442%	$30.0059	$30.01	$30.00	$30.00
Purchase #5	$87.31	10.851%	$96.784	$96.78	$96.80	$96.80
Purchase #6	$35.92	6.325%	$38.1919	$38.19	$38.20	$38.20
Purchase #7	$169.72	8.144%	$183.542	$183.54	$183.55	$183.50
7 purchase totals =	$682.82		$741.1972	$741.19	$741.20	$741.20