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 $88.52   5.762%   $93.6205   $93.62   $93.60   $93.60  
  Purchase #2 $62.45   4.815%   $65.457   $65.46   $65.45   $65.50  
  Purchase #3 $48.51   5.239%   $51.0514   $51.05   $51.05   $51.10  
  Purchase #4 $188.89   9.410%   $206.6645   $206.66   $206.65   $206.70  
  Purchase #5 $124.77   5.207%   $131.2668   $131.27   $131.25   $131.30  
  Purchase #6 $138.78   5.633%   $146.5975   $146.60   $146.60   $146.60  
  Purchase #7 $80.51   8.865%   $87.6472   $87.65   $87.65   $87.60  
  7 purchase totals = $732.43       $782.3049   $782.31   $782.25   $782.40