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 $215.94   5.275%   $227.3308   $227.33   $227.35   $227.30  
  Purchase #2 $220.86   6.618%   $235.4765   $235.48   $235.50   $235.50  
  Purchase #3 $116.32   4.635%   $121.7114   $121.71   $121.70   $121.70  
  Purchase #4 $214.57   5.306%   $225.9551   $225.96   $225.95   $226.00  
  Purchase #5 $76.95   6.699%   $82.1049   $82.10   $82.10   $82.10  
  Purchase #6 $167.39   8.508%   $181.6315   $181.63   $181.65   $181.60  
  Purchase #7 $162.36   5.870%   $171.8905   $171.89   $171.90   $171.90  
  7 purchase totals = $1,174.39       $1,246.1007   $1,246.10   $1,246.15   $1,246.10