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 $58.95   11.292%   $65.6066   $65.61   $65.60   $65.60  
  Purchase #2 $229.36   13.229%   $259.702   $259.70   $259.70   $259.70  
  Purchase #3 $217.54   13.172%   $246.1944   $246.19   $246.20   $246.20  
  Purchase #4 $64.91   12.389%   $72.9517   $72.95   $72.95   $73.00  
  Purchase #5 $84.40   5.617%   $89.1407   $89.14   $89.15   $89.10  
  Purchase #6 $148.51   8.192%   $160.6759   $160.68   $160.70   $160.70  
  Purchase #7 $64.52   5.415%   $68.0138   $68.01   $68.00   $68.00  
  7 purchase totals = $868.19       $962.2851   $962.28   $962.30   $962.30