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 $93.81   5.330%   $98.8101   $98.81   $98.80   $98.80  
  Purchase #2 $166.70   8.603%   $181.0412   $181.04   $181.05   $181.00  
  Purchase #3 $227.31   11.304%   $253.0051   $253.01   $253.00   $253.00  
  Purchase #4 $98.41   8.362%   $106.639   $106.64   $106.65   $106.60  
  Purchase #5 $131.66   3.685%   $136.5117   $136.51   $136.50   $136.50  
  Purchase #6 $199.68   4.657%   $208.9791   $208.98   $209.00   $209.00  
  Purchase #7 $199.65   8.708%   $217.0355   $217.04   $217.05   $217.00  
  7 purchase totals = $1,117.22       $1,202.0217   $1,202.03   $1,202.05   $1,201.90