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 $103.62   3.316%   $107.056   $107.06   $107.05   $107.10  
  Purchase #2 $101.27   9.239%   $110.6263   $110.63   $110.65   $110.60  
  Purchase #3 $130.29   7.562%   $140.1425   $140.14   $140.15   $140.10  
  Purchase #4 $153.84   8.802%   $167.381   $167.38   $167.40   $167.40  
  Purchase #5 $193.57   9.732%   $212.4082   $212.41   $212.40   $212.40  
  Purchase #6 $222.44   12.354%   $249.9202   $249.92   $249.90   $249.90  
  Purchase #7 $62.25   5.143%   $65.4515   $65.45   $65.45   $65.50  
  7 purchase totals = $967.28       $1,052.9857   $1,052.99   $1,053.00   $1,053.00