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 $212.53   5.360%   $223.9216   $223.92   $223.90   $223.90  
  Purchase #2 $198.94   3.824%   $206.5475   $206.55   $206.55   $206.50  
  Purchase #3 $77.41   6.815%   $82.6855   $82.69   $82.70   $82.70  
  Purchase #4 $193.52   8.110%   $209.2145   $209.21   $209.20   $209.20  
  Purchase #5 $220.31   8.330%   $238.6618   $238.66   $238.65   $238.70  
  Purchase #6 $164.71   6.484%   $175.3898   $175.39   $175.40   $175.40  
  Purchase #7 $196.88   7.404%   $211.457   $211.46   $211.45   $211.50  
  7 purchase totals = $1,264.30       $1,347.8777   $1,347.88   $1,347.85   $1,347.90