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 $163.82   7.178%   $175.579   $175.58   $175.60   $175.60  
  Purchase #2 $119.47   5.281%   $125.7792   $125.78   $125.80   $125.80  
  Purchase #3 $15.56   6.499%   $16.5712   $16.57   $16.55   $16.60  
  Purchase #4 $173.77   13.686%   $197.5522   $197.55   $197.55   $197.60  
  Purchase #5 $45.38   7.287%   $48.6868   $48.69   $48.70   $48.70  
  Purchase #6 $241.81   7.606%   $260.2021   $260.20   $260.20   $260.20  
  Purchase #7 $228.49   10.342%   $252.1204   $252.12   $252.10   $252.10  
  7 purchase totals = $988.30       $1,076.4909   $1,076.49   $1,076.50   $1,076.60