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 $86.48   10.628%   $95.6711   $95.67   $95.65   $95.70  
  Purchase #2 $124.75   13.653%   $141.7821   $141.78   $141.80   $141.80  
  Purchase #3 $110.48   13.423%   $125.3097   $125.31   $125.30   $125.30  
  Purchase #4 $59.61   11.777%   $66.6303   $66.63   $66.65   $66.60  
  Purchase #5 $218.48   10.335%   $241.0599   $241.06   $241.05   $241.10  
  Purchase #6 $104.58   3.293%   $108.0238   $108.02   $108.00   $108.00  
  Purchase #7 $203.32   13.497%   $230.7621   $230.76   $230.75   $230.80  
  7 purchase totals = $907.70       $1,009.2390   $1,009.23   $1,009.20   $1,009.30