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 $58.89   10.427%   $65.0305   $65.03   $65.05   $65.00  
  Purchase #2 $104.45   6.855%   $111.61   $111.61   $111.60   $111.60  
  Purchase #3 $199.88   6.820%   $213.5118   $213.51   $213.50   $213.50  
  Purchase #4 $167.62   8.566%   $181.9783   $181.98   $182.00   $182.00  
  Purchase #5 $94.81   8.219%   $102.6024   $102.60   $102.60   $102.60  
  Purchase #6 $150.45   3.183%   $155.2388   $155.24   $155.25   $155.20  
  Purchase #7 $23.52   11.265%   $26.1695   $26.17   $26.15   $26.20  
  7 purchase totals = $799.62       $856.1413   $856.14   $856.15   $856.10