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	$153.69	7.293%	$164.8986	$164.90	$164.90	$164.90
Purchase #2	$190.26	12.800%	$214.6133	$214.61	$214.60	$214.60
Purchase #3	$95.62	8.276%	$103.5335	$103.53	$103.55	$103.50
Purchase #4	$189.39	12.371%	$212.8194	$212.82	$212.80	$212.80
Purchase #5	$180.96	9.379%	$197.9322	$197.93	$197.95	$197.90
Purchase #6	$121.54	5.280%	$127.9573	$127.96	$127.95	$128.00
Purchase #7	$87.59	3.271%	$90.4551	$90.46	$90.45	$90.50
7 purchase totals =	$1,019.05		$1,112.2094	$1,112.21	$1,112.20	$1,112.20