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 $83.90   13.546%   $95.2651   $95.27   $95.25   $95.30  
  Purchase #2 $206.27   8.407%   $223.6111   $223.61   $223.60   $223.60  
  Purchase #3 $228.64   10.433%   $252.494   $252.49   $252.50   $252.50  
  Purchase #4 $236.61   6.783%   $252.6593   $252.66   $252.65   $252.70  
  Purchase #5 $86.82   13.766%   $98.7716   $98.77   $98.75   $98.80  
  Purchase #6 $136.76   10.307%   $150.8559   $150.86   $150.85   $150.90  
  Purchase #7 $79.64   11.302%   $88.6409   $88.64   $88.65   $88.60  
  7 purchase totals = $1,058.64       $1,162.2979   $1,162.30   $1,162.25   $1,162.40