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	$222.33	13.135%	$251.533	$251.53	$251.55	$251.50
Purchase #2	$139.89	12.127%	$156.8545	$156.85	$156.85	$156.90
Purchase #3	$196.61	13.218%	$222.5979	$222.60	$222.60	$222.60
Purchase #4	$87.65	9.678%	$96.1328	$96.13	$96.15	$96.10
Purchase #5	$170.98	3.204%	$176.4582	$176.46	$176.45	$176.50
Purchase #6	$219.76	9.864%	$241.4371	$241.44	$241.45	$241.40
Purchase #7	$125.82	13.218%	$142.4509	$142.45	$142.45	$142.50
7 purchase totals =	$1,163.04		$1,287.4644	$1,287.46	$1,287.50	$1,287.50