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 $46.32   3.529%   $47.9546   $47.95   $47.95   $48.00  
  Purchase #2 $207.31   10.599%   $229.2828   $229.28   $229.30   $229.30  
  Purchase #3 $48.95   12.645%   $55.1397   $55.14   $55.15   $55.10  
  Purchase #4 $87.70   13.718%   $99.7307   $99.73   $99.75   $99.70  
  Purchase #5 $36.41   5.460%   $38.398   $38.40   $38.40   $38.40  
  Purchase #6 $193.66   4.825%   $203.0041   $203.00   $203.00   $203.00  
  Purchase #7 $235.70   11.191%   $262.0772   $262.08   $262.10   $262.10  
  7 purchase totals = $856.05       $935.5871   $935.58   $935.65   $935.60