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	$152.65	12.595%	$171.8763	$171.88	$171.90	$171.90
Purchase #2	$109.45	9.322%	$119.6529	$119.65	$119.65	$119.70
Purchase #3	$63.26	12.359%	$71.0783	$71.08	$71.10	$71.10
Purchase #4	$131.34	13.137%	$148.5941	$148.59	$148.60	$148.60
Purchase #5	$78.63	9.548%	$86.1376	$86.14	$86.15	$86.10
Purchase #6	$60.35	8.600%	$65.5401	$65.54	$65.55	$65.50
Purchase #7	$142.25	6.622%	$151.6698	$151.67	$151.65	$151.70
7 purchase totals =	$737.93		$814.5491	$814.55	$814.60	$814.60