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 $53.48   13.438%   $60.6666   $60.67   $60.65   $60.70  
  Purchase #2 $166.25   6.688%   $177.3688   $177.37   $177.35   $177.40  
  Purchase #3 $27.60   11.444%   $30.7585   $30.76   $30.75   $30.80  
  Purchase #4 $211.83   10.293%   $233.6337   $233.63   $233.65   $233.60  
  Purchase #5 $31.41   11.870%   $35.1384   $35.14   $35.15   $35.10  
  Purchase #6 $223.35   4.197%   $232.724   $232.72   $232.70   $232.70  
  Purchase #7 $120.60   3.795%   $125.1768   $125.18   $125.20   $125.20  
  7 purchase totals = $834.52       $895.4668   $895.47   $895.45   $895.50