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 $147.54   13.821%   $167.9315   $167.93   $167.95   $167.90  
  Purchase #2 $25.44   5.566%   $26.856   $26.86   $26.85   $26.90  
  Purchase #3 $43.45   10.329%   $47.938   $47.94   $47.95   $47.90  
  Purchase #4 $82.97   6.871%   $88.6709   $88.67   $88.65   $88.70  
  Purchase #5 $222.97   5.692%   $235.6615   $235.66   $235.65   $235.70  
  Purchase #6 $232.89   12.718%   $262.509   $262.51   $262.50   $262.50  
  Purchase #7 $112.82   11.260%   $125.5235   $125.52   $125.50   $125.50  
  7 purchase totals = $868.08       $955.0904   $955.09   $955.05   $955.10