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	$104.44	6.456%	$111.1826	$111.18	$111.20	$111.20
Purchase #2	$180.30	9.161%	$196.8173	$196.82	$196.80	$196.80
Purchase #3	$47.31	10.858%	$52.4469	$52.45	$52.45	$52.40
Purchase #4	$150.45	9.604%	$164.8992	$164.90	$164.90	$164.90
Purchase #5	$222.66	3.728%	$230.9608	$230.96	$230.95	$231.00
Purchase #6	$29.93	3.670%	$31.0284	$31.03	$31.05	$31.00
Purchase #7	$193.60	6.513%	$206.2092	$206.21	$206.20	$206.20
7 purchase totals =	$928.69		$993.5444	$993.55	$993.55	$993.50