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 $51.42   5.142%   $54.064   $54.06   $54.05   $54.10  
  Purchase #2 $235.76   5.582%   $248.9201   $248.92   $248.90   $248.90  
  Purchase #3 $100.31   13.217%   $113.568   $113.57   $113.55   $113.60  
  Purchase #4 $16.39   6.434%   $17.4445   $17.44   $17.45   $17.40  
  Purchase #5 $221.99   6.516%   $236.4549   $236.45   $236.45   $236.50  
  Purchase #6 $143.92   5.203%   $151.4082   $151.41   $151.40   $151.40  
  Purchase #7 $178.28   13.377%   $202.1285   $202.13   $202.15   $202.10  
  7 purchase totals = $948.07       $1,023.9882   $1,023.98   $1,023.95   $1,024.00