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	$192.38	12.508%	$216.4429	$216.44	$216.45	$216.40
Purchase #2	$71.46	12.241%	$80.2074	$80.21	$80.20	$80.20
Purchase #3	$128.95	9.123%	$140.7141	$140.71	$140.70	$140.70
Purchase #4	$168.63	11.202%	$187.5199	$187.52	$187.50	$187.50
Purchase #5	$160.25	11.758%	$179.0922	$179.09	$179.10	$179.10
Purchase #6	$52.36	5.168%	$55.066	$55.07	$55.05	$55.10
Purchase #7	$154.68	3.526%	$160.134	$160.13	$160.15	$160.10
7 purchase totals =	$928.71		$1,019.1765	$1,019.17	$1,019.15	$1,019.10