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 $65.92   8.121%   $71.2734   $71.27   $71.25   $71.30  
  Purchase #2 $238.52   10.706%   $264.056   $264.06   $264.05   $264.10  
  Purchase #3 $227.47   8.452%   $246.6958   $246.70   $246.70   $246.70  
  Purchase #4 $181.99   9.639%   $199.532   $199.53   $199.55   $199.50  
  Purchase #5 $249.80   7.769%   $269.207   $269.21   $269.20   $269.20  
  Purchase #6 $46.54   13.274%   $52.7177   $52.72   $52.70   $52.70  
  Purchase #7 $59.46   10.782%   $65.871   $65.87   $65.85   $65.90  
  7 purchase totals = $1,069.70       $1,169.3529   $1,169.36   $1,169.30   $1,169.40