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	$68.64	3.659%	$71.1515	$71.15	$71.15	$71.20
Purchase #2	$205.38	8.333%	$222.4943	$222.49	$222.50	$222.50
Purchase #3	$124.63	5.462%	$131.4373	$131.44	$131.45	$131.40
Purchase #4	$226.49	10.539%	$250.3598	$250.36	$250.35	$250.40
Purchase #5	$52.68	3.172%	$54.351	$54.35	$54.35	$54.40
Purchase #6	$139.39	6.604%	$148.5953	$148.60	$148.60	$148.60
Purchase #7	$153.36	7.475%	$164.8237	$164.82	$164.80	$164.80
7 purchase totals =	$970.57		$1,043.2129	$1,043.21	$1,043.20	$1,043.30