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 $88.47   7.448%   $95.0592   $95.06   $95.05   $95.10  
  Purchase #2 $179.79   9.397%   $196.6849   $196.68   $196.70   $196.70  
  Purchase #3 $33.78   5.205%   $35.5382   $35.54   $35.55   $35.50  
  Purchase #4 $71.69   9.152%   $78.2511   $78.25   $78.25   $78.30  
  Purchase #5 $136.29   3.718%   $141.3573   $141.36   $141.35   $141.40  
  Purchase #6 $225.29   4.400%   $235.2028   $235.20   $235.20   $235.20  
  Purchase #7 $41.32   8.126%   $44.6777   $44.68   $44.70   $44.70  
  7 purchase totals = $776.63       $826.7712   $826.77   $826.80   $826.90