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	$125.31	13.681%	$142.4537	$142.45	$142.45	$142.50
Purchase #2	$116.50	13.221%	$131.9025	$131.90	$131.90	$131.90
Purchase #3	$206.88	5.739%	$218.7528	$218.75	$218.75	$218.80
Purchase #4	$151.88	12.278%	$170.5278	$170.53	$170.55	$170.50
Purchase #5	$22.96	4.749%	$24.0504	$24.05	$24.05	$24.10
Purchase #6	$240.98	3.767%	$250.0577	$250.06	$250.05	$250.10
Purchase #7	$185.29	7.241%	$198.7068	$198.71	$198.70	$198.70
7 purchase totals =	$1,049.80		$1,136.4517	$1,136.45	$1,136.45	$1,136.60