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	$233.72	12.501%	$262.9373	$262.94	$262.95	$262.90
Purchase #2	$36.71	6.504%	$39.0976	$39.10	$39.10	$39.10
Purchase #3	$126.94	12.645%	$142.9916	$142.99	$143.00	$143.00
Purchase #4	$67.85	7.132%	$72.6891	$72.69	$72.70	$72.70
Purchase #5	$230.79	13.323%	$261.5382	$261.54	$261.55	$261.50
Purchase #6	$37.98	12.208%	$42.6166	$42.62	$42.60	$42.60
Purchase #7	$83.50	3.256%	$86.2188	$86.22	$86.20	$86.20
7 purchase totals =	$817.49		$908.0892	$908.10	$908.10	$908.00