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 $86.62   10.458%   $95.6787   $95.68   $95.70   $95.70  
  Purchase #2 $45.69   5.783%   $48.3323   $48.33   $48.35   $48.30  
  Purchase #3 $228.95   9.858%   $251.5199   $251.52   $251.50   $251.50  
  Purchase #4 $249.51   5.776%   $263.9217   $263.92   $263.90   $263.90  
  Purchase #5 $170.98   3.334%   $176.6805   $176.68   $176.70   $176.70  
  Purchase #6 $227.37   12.465%   $255.7117   $255.71   $255.70   $255.70  
  Purchase #7 $15.75   8.656%   $17.1133   $17.11   $17.10   $17.10  
  7 purchase totals = $1,024.87       $1,108.9581   $1,108.95   $1,108.95   $1,108.90