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 $197.56   4.778%   $206.9994   $207.00   $207.00   $207.00  
  Purchase #2 $91.62   13.836%   $104.2965   $104.30   $104.30   $104.30  
  Purchase #3 $133.40   7.849%   $143.8706   $143.87   $143.85   $143.90  
  Purchase #4 $135.64   11.111%   $150.711   $150.71   $150.70   $150.70  
  Purchase #5 $227.58   5.572%   $240.2608   $240.26   $240.25   $240.30  
  Purchase #6 $10.84   3.158%   $11.1823   $11.18   $11.20   $11.20  
  Purchase #7 $174.92   13.558%   $198.6357   $198.64   $198.65   $198.60  
  7 purchase totals = $971.56       $1,055.9563   $1,055.96   $1,055.95   $1,056.00