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	$32.52	8.759%	$35.3684	$35.37	$35.35	$35.40
Purchase #2	$88.38	11.387%	$98.4438	$98.44	$98.45	$98.40
Purchase #3	$189.81	4.783%	$198.8886	$198.89	$198.90	$198.90
Purchase #4	$131.48	10.341%	$145.0763	$145.08	$145.10	$145.10
Purchase #5	$148.51	11.824%	$166.0698	$166.07	$166.05	$166.10
Purchase #6	$185.26	3.150%	$191.0957	$191.10	$191.10	$191.10
Purchase #7	$73.29	6.858%	$78.3162	$78.32	$78.30	$78.30
7 purchase totals =	$849.25		$913.2588	$913.27	$913.25	$913.30