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 $60.63   11.406%   $67.5455   $67.55   $67.55   $67.50  
  Purchase #2 $56.68   9.622%   $62.1337   $62.13   $62.15   $62.10  
  Purchase #3 $183.83   8.593%   $199.6265   $199.63   $199.65   $199.60  
  Purchase #4 $177.52   8.870%   $193.266   $193.27   $193.25   $193.30  
  Purchase #5 $161.76   9.674%   $177.4087   $177.41   $177.40   $177.40  
  Purchase #6 $181.27   4.704%   $189.7969   $189.80   $189.80   $189.80  
  Purchase #7 $206.60   7.831%   $222.7788   $222.78   $222.80   $222.80  
  7 purchase totals = $1,028.29       $1,112.5561   $1,112.57   $1,112.60   $1,112.50