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 $191.71   4.725%   $200.7683   $200.77   $200.75   $200.80  
  Purchase #2 $216.95   7.779%   $233.8265   $233.83   $233.85   $233.80  
  Purchase #3 $152.95   4.713%   $160.1585   $160.16   $160.15   $160.20  
  Purchase #4 $66.34   10.849%   $73.5372   $73.54   $73.55   $73.50  
  Purchase #5 $234.94   6.564%   $250.3615   $250.36   $250.35   $250.40  
  Purchase #6 $5.32   13.279%   $6.0264   $6.03   $6.05   $6.00  
  Purchase #7 $210.49   12.435%   $236.6644   $236.66   $236.65   $236.70  
  7 purchase totals = $1,078.70       $1,161.3428   $1,161.35   $1,161.35   $1,161.40