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 $118.41   6.349%   $125.9279   $125.93   $125.95   $125.90  
  Purchase #2 $216.73   5.408%   $228.4508   $228.45   $228.45   $228.50  
  Purchase #3 $123.90   3.266%   $127.9466   $127.95   $127.95   $127.90  
  Purchase #4 $134.90   13.459%   $153.0562   $153.06   $153.05   $153.10  
  Purchase #5 $127.92   12.486%   $143.8921   $143.89   $143.90   $143.90  
  Purchase #6 $164.74   3.548%   $170.585   $170.59   $170.60   $170.60  
  Purchase #7 $93.32   12.291%   $104.79   $104.79   $104.80   $104.80  
  7 purchase totals = $979.92       $1,054.6486   $1,054.66   $1,054.70   $1,054.70