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 $95.49   10.725%   $105.7313   $105.73   $105.75   $105.70  
  Purchase #2 $201.53   8.283%   $218.2227   $218.22   $218.20   $218.20  
  Purchase #3 $199.64   3.650%   $206.9269   $206.93   $206.95   $206.90  
  Purchase #4 $111.30   7.642%   $119.8055   $119.81   $119.80   $119.80  
  Purchase #5 $235.60   9.363%   $257.6592   $257.66   $257.65   $257.70  
  Purchase #6 $217.29   6.533%   $231.4856   $231.49   $231.50   $231.50  
  Purchase #7 $150.84   4.119%   $157.0531   $157.05   $157.05   $157.10  
  7 purchase totals = $1,211.69       $1,296.8843   $1,296.89   $1,296.90   $1,296.90