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	$229.25	11.478%	$255.5633	$255.56	$255.55	$255.60
Purchase #2	$176.31	9.292%	$192.6927	$192.69	$192.70	$192.70
Purchase #3	$131.63	5.772%	$139.2277	$139.23	$139.25	$139.20
Purchase #4	$208.40	3.594%	$215.8899	$215.89	$215.90	$215.90
Purchase #5	$203.49	6.259%	$216.2264	$216.23	$216.25	$216.20
Purchase #6	$200.74	11.167%	$223.1566	$223.16	$223.15	$223.20
Purchase #7	$31.55	8.794%	$34.3245	$34.32	$34.30	$34.30
7 purchase totals =	$1,181.37		$1,277.0811	$1,277.08	$1,277.10	$1,277.10