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 $213.42   11.461%   $237.8801   $237.88   $237.90   $237.90  
  Purchase #2 $247.31   12.281%   $277.6821   $277.68   $277.70   $277.70  
  Purchase #3 $96.31   8.609%   $104.6013   $104.60   $104.60   $104.60  
  Purchase #4 $43.29   7.822%   $46.6761   $46.68   $46.70   $46.70  
  Purchase #5 $119.68   9.303%   $130.8138   $130.81   $130.80   $130.80  
  Purchase #6 $98.41   7.301%   $105.5949   $105.59   $105.60   $105.60  
  Purchase #7 $230.70   12.769%   $260.1581   $260.16   $260.15   $260.20  
  7 purchase totals = $1,049.12       $1,163.4064   $1,163.40   $1,163.45   $1,163.50