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 $214.25   4.178%   $223.2014   $223.20   $223.20   $223.20  
  Purchase #2 $76.87   10.616%   $85.0305   $85.03   $85.05   $85.00  
  Purchase #3 $115.65   9.470%   $126.6021   $126.60   $126.60   $126.60  
  Purchase #4 $191.73   10.847%   $212.527   $212.53   $212.55   $212.50  
  Purchase #5 $212.77   13.849%   $242.2365   $242.24   $242.25   $242.20  
  Purchase #6 $119.72   4.426%   $125.0188   $125.02   $125.00   $125.00  
  Purchase #7 $234.61   5.370%   $247.2086   $247.21   $247.20   $247.20  
  7 purchase totals = $1,165.60       $1,261.8249   $1,261.83   $1,261.85   $1,261.70