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 $116.27   7.581%   $125.0844   $125.08   $125.10   $125.10  
  Purchase #2 $194.69   10.354%   $214.8482   $214.85   $214.85   $214.80  
  Purchase #3 $227.32   7.810%   $245.0737   $245.07   $245.05   $245.10  
  Purchase #4 $214.72   6.265%   $228.1722   $228.17   $228.15   $228.20  
  Purchase #5 $79.86   3.648%   $82.7733   $82.77   $82.75   $82.80  
  Purchase #6 $33.97   3.200%   $35.057   $35.06   $35.05   $35.10  
  Purchase #7 $109.63   10.850%   $121.5249   $121.52   $121.50   $121.50  
  7 purchase totals = $976.46       $1,052.5337   $1,052.52   $1,052.45   $1,052.60