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 $182.53   6.459%   $194.3196   $194.32   $194.30   $194.30  
  Purchase #2 $226.34   3.708%   $234.7327   $234.73   $234.75   $234.70  
  Purchase #3 $8.33   13.254%   $9.4341   $9.43   $9.45   $9.40  
  Purchase #4 $235.95   4.622%   $246.8556   $246.86   $246.85   $246.90  
  Purchase #5 $10.63   4.160%   $11.0722   $11.07   $11.05   $11.10  
  Purchase #6 $59.92   7.781%   $64.5824   $64.58   $64.60   $64.60  
  Purchase #7 $232.66   10.689%   $257.529   $257.53   $257.55   $257.50  
  7 purchase totals = $956.36       $1,018.5256   $1,018.52   $1,018.55   $1,018.50