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 $98.82   7.315%   $106.0487   $106.05   $106.05   $106.00  
  Purchase #2 $246.66   5.179%   $259.4345   $259.43   $259.45   $259.40  
  Purchase #3 $62.73   4.505%   $65.556   $65.56   $65.55   $65.60  
  Purchase #4 $217.98   5.196%   $229.3062   $229.31   $229.30   $229.30  
  Purchase #5 $86.34   8.397%   $93.59   $93.59   $93.60   $93.60  
  Purchase #6 $23.32   13.611%   $26.4941   $26.49   $26.50   $26.50  
  Purchase #7 $66.29   13.446%   $75.2034   $75.20   $75.20   $75.20  
  7 purchase totals = $802.14       $855.6329   $855.63   $855.65   $855.60