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	$67.58	11.527%	$75.3699	$75.37	$75.35	$75.40
Purchase #2	$14.53	3.732%	$15.0723	$15.07	$15.05	$15.10
Purchase #3	$228.43	11.713%	$255.186	$255.19	$255.20	$255.20
Purchase #4	$150.26	9.467%	$164.4851	$164.49	$164.50	$164.50
Purchase #5	$86.62	10.559%	$95.7662	$95.77	$95.75	$95.80
Purchase #6	$71.69	6.223%	$76.1513	$76.15	$76.15	$76.20
Purchase #7	$122.71	4.218%	$127.8859	$127.89	$127.90	$127.90
7 purchase totals =	$741.82		$809.9167	$809.93	$809.90	$810.10