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	$214.61	11.853%	$240.0477	$240.05	$240.05	$240.00
Purchase #2	$17.38	4.816%	$18.217	$18.22	$18.20	$18.20
Purchase #3	$50.54	10.333%	$55.7623	$55.76	$55.75	$55.80
Purchase #4	$178.54	12.302%	$200.504	$200.50	$200.50	$200.50
Purchase #5	$105.66	11.847%	$118.1775	$118.18	$118.20	$118.20
Purchase #6	$190.73	9.214%	$208.3039	$208.30	$208.30	$208.30
Purchase #7	$40.49	4.768%	$42.4206	$42.42	$42.40	$42.40
7 purchase totals =	$797.95		$883.4330	$883.43	$883.40	$883.40