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	$196.34	8.392%	$212.8169	$212.82	$212.80	$212.80
Purchase #2	$39.27	3.378%	$40.5965	$40.60	$40.60	$40.60
Purchase #3	$122.67	12.127%	$137.5462	$137.55	$137.55	$137.50
Purchase #4	$183.95	13.815%	$209.3627	$209.36	$209.35	$209.40
Purchase #5	$157.77	10.508%	$174.3485	$174.35	$174.35	$174.30
Purchase #6	$216.81	9.787%	$238.0292	$238.03	$238.05	$238.00
Purchase #7	$143.72	9.112%	$156.8158	$156.82	$156.80	$156.80
7 purchase totals =	$1,060.53		$1,169.5158	$1,169.53	$1,169.50	$1,169.40