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	$76.92	13.871%	$87.5896	$87.59	$87.60	$87.60
Purchase #2	$65.85	8.643%	$71.5414	$71.54	$71.55	$71.50
Purchase #3	$182.83	9.683%	$200.5334	$200.53	$200.55	$200.50
Purchase #4	$85.94	4.591%	$89.8855	$89.89	$89.90	$89.90
Purchase #5	$186.61	7.251%	$200.1411	$200.14	$200.15	$200.10
Purchase #6	$214.82	4.763%	$225.0519	$225.05	$225.05	$225.10
Purchase #7	$232.99	9.375%	$254.8328	$254.83	$254.85	$254.80
7 purchase totals =	$1,045.96		$1,129.5757	$1,129.57	$1,129.65	$1,129.50