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	$87.75	4.725%	$91.8962	$91.90	$91.90	$91.90
Purchase #2	$186.81	12.813%	$210.746	$210.75	$210.75	$210.70
Purchase #3	$93.41	9.754%	$102.5212	$102.52	$102.50	$102.50
Purchase #4	$35.91	12.364%	$40.3499	$40.35	$40.35	$40.30
Purchase #5	$101.47	13.232%	$114.8965	$114.90	$114.90	$114.90
Purchase #6	$106.28	13.750%	$120.8935	$120.89	$120.90	$120.90
Purchase #7	$45.26	13.724%	$51.4715	$51.47	$51.45	$51.50
7 purchase totals =	$656.89		$732.7748	$732.78	$732.75	$732.70