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 $97.25   10.488%   $107.4496   $107.45   $107.45   $107.40  
  Purchase #2 $144.42   11.547%   $161.0962   $161.10   $161.10   $161.10  
  Purchase #3 $44.62   8.692%   $48.4984   $48.50   $48.50   $48.50  
  Purchase #4 $103.42   9.635%   $113.3845   $113.38   $113.40   $113.40  
  Purchase #5 $52.51   10.361%   $57.9506   $57.95   $57.95   $58.00  
  Purchase #6 $62.69   4.417%   $65.459   $65.46   $65.45   $65.50  
  Purchase #7 $198.51   11.835%   $222.0037   $222.00   $222.00   $222.00  
  7 purchase totals = $703.42       $775.8420   $775.84   $775.85   $775.90