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 $214.91   10.418%   $237.2993   $237.30   $237.30   $237.30  
  Purchase #2 $240.65   7.153%   $257.8637   $257.86   $257.85   $257.90  
  Purchase #3 $139.28   10.522%   $153.935   $153.94   $153.95   $153.90  
  Purchase #4 $211.86   10.475%   $234.0523   $234.05   $234.05   $234.10  
  Purchase #5 $229.38   4.197%   $239.0071   $239.01   $239.00   $239.00  
  Purchase #6 $181.48   13.268%   $205.5588   $205.56   $205.55   $205.60  
  Purchase #7 $68.27   7.376%   $73.3056   $73.31   $73.30   $73.30  
  7 purchase totals = $1,285.83       $1,401.0218   $1,401.03   $1,401.00   $1,401.10