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	$143.89	8.418%	$156.0027	$156.00	$156.00	$156.00
Purchase #2	$94.45	6.386%	$100.4816	$100.48	$100.50	$100.50
Purchase #3	$179.70	5.726%	$189.9896	$189.99	$190.00	$190.00
Purchase #4	$147.89	13.750%	$168.2249	$168.22	$168.20	$168.20
Purchase #5	$152.27	8.284%	$164.884	$164.88	$164.90	$164.90
Purchase #6	$51.75	5.357%	$54.5222	$54.52	$54.50	$54.50
Purchase #7	$136.35	11.794%	$152.4311	$152.43	$152.45	$152.40
7 purchase totals =	$906.30		$986.5361	$986.52	$986.55	$986.50