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 $84.28   11.232%   $93.7463   $93.75   $93.75   $93.70  
  Purchase #2 $105.83   11.231%   $117.7158   $117.72   $117.70   $117.70  
  Purchase #3 $215.74   11.134%   $239.7605   $239.76   $239.75   $239.80  
  Purchase #4 $147.69   7.444%   $158.684   $158.68   $158.70   $158.70  
  Purchase #5 $203.95   7.216%   $218.667   $218.67   $218.65   $218.70  
  Purchase #6 $57.74   5.322%   $60.8129   $60.81   $60.80   $60.80  
  Purchase #7 $127.51   13.430%   $144.6346   $144.63   $144.65   $144.60  
  7 purchase totals = $942.74       $1,034.0211   $1,034.02   $1,034.00   $1,034.00