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	$230.86	13.443%	$261.8945	$261.89	$261.90	$261.90
Purchase #2	$250.55	6.575%	$267.0237	$267.02	$267.00	$267.00
Purchase #3	$144.32	8.573%	$156.6926	$156.69	$156.70	$156.70
Purchase #4	$123.70	6.588%	$131.8494	$131.85	$131.85	$131.80
Purchase #5	$155.87	7.102%	$166.9399	$166.94	$166.95	$166.90
Purchase #6	$143.53	5.530%	$151.4672	$151.47	$151.45	$151.50
Purchase #7	$236.74	12.622%	$266.6213	$266.62	$266.60	$266.60
7 purchase totals =	$1,285.57		$1,402.4886	$1,402.48	$1,402.45	$1,402.40