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 $64.66   11.281%   $71.9543   $71.95   $71.95   $72.00  
  Purchase #2 $198.56   13.653%   $225.6694   $225.67   $225.65   $225.70  
  Purchase #3 $212.31   11.712%   $237.1757   $237.18   $237.20   $237.20  
  Purchase #4 $170.90   10.307%   $188.5147   $188.51   $188.50   $188.50  
  Purchase #5 $100.99   3.861%   $104.8892   $104.89   $104.90   $104.90  
  Purchase #6 $238.88   12.309%   $268.2837   $268.28   $268.30   $268.30  
  Purchase #7 $10.41   5.202%   $10.9515   $10.95   $10.95   $11.00  
  7 purchase totals = $996.71       $1,107.4385   $1,107.43   $1,107.45   $1,107.60