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 $179.34   8.169%   $193.9903   $193.99   $194.00   $194.00  
  Purchase #2 $127.28   5.524%   $134.3109   $134.31   $134.30   $134.30  
  Purchase #3 $67.38   9.745%   $73.9462   $73.95   $73.95   $73.90  
  Purchase #4 $236.57   13.604%   $268.753   $268.75   $268.75   $268.80  
  Purchase #5 $222.58   12.679%   $250.8009   $250.80   $250.80   $250.80  
  Purchase #6 $206.55   6.670%   $220.3269   $220.33   $220.35   $220.30  
  Purchase #7 $60.68   5.338%   $63.9191   $63.92   $63.90   $63.90  
  7 purchase totals = $1,100.38       $1,206.0473   $1,206.05   $1,206.05   $1,206.00