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	$203.43	12.271%	$228.3929	$228.39	$228.40	$228.40
Purchase #2	$17.98	7.340%	$19.2997	$19.30	$19.30	$19.30
Purchase #3	$212.35	5.266%	$223.5324	$223.53	$223.55	$223.50
Purchase #4	$63.56	4.723%	$66.5619	$66.56	$66.55	$66.60
Purchase #5	$168.89	12.417%	$189.8611	$189.86	$189.85	$189.90
Purchase #6	$138.32	11.644%	$154.426	$154.43	$154.45	$154.40
Purchase #7	$180.55	3.167%	$186.268	$186.27	$186.25	$186.30
7 purchase totals =	$985.08		$1,068.3420	$1,068.34	$1,068.35	$1,068.40