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 $182.48   7.437%   $196.051   $196.05   $196.05   $196.10  
  Purchase #2 $233.28   4.143%   $242.9448   $242.94   $242.95   $242.90  
  Purchase #3 $213.55   8.687%   $232.1011   $232.10   $232.10   $232.10  
  Purchase #4 $226.63   8.638%   $246.2063   $246.21   $246.20   $246.20  
  Purchase #5 $171.47   3.232%   $177.0119   $177.01   $177.00   $177.00  
  Purchase #6 $79.25   5.612%   $83.6975   $83.70   $83.70   $83.70  
  Purchase #7 $159.63   8.788%   $173.6583   $173.66   $173.65   $173.70  
  7 purchase totals = $1,266.29       $1,351.6709   $1,351.67   $1,351.65   $1,351.70