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	$213.25	3.409%	$220.5197	$220.52	$220.50	$220.50
Purchase #2	$35.58	13.691%	$40.4513	$40.45	$40.45	$40.50
Purchase #3	$142.38	5.682%	$150.47	$150.47	$150.45	$150.50
Purchase #4	$248.27	3.592%	$257.1879	$257.19	$257.20	$257.20
Purchase #5	$190.95	13.172%	$216.1019	$216.10	$216.10	$216.10
Purchase #6	$95.27	9.491%	$104.3121	$104.31	$104.30	$104.30
Purchase #7	$22.52	8.767%	$24.4943	$24.49	$24.50	$24.50
7 purchase totals =	$948.22		$1,013.5372	$1,013.53	$1,013.50	$1,013.60