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 $207.76   13.749%   $236.3249   $236.32   $236.30   $236.30  
  Purchase #2 $31.71   10.559%   $35.0583   $35.06   $35.05   $35.10  
  Purchase #3 $169.52   10.681%   $187.6264   $187.63   $187.65   $187.60  
  Purchase #4 $142.69   10.393%   $157.5198   $157.52   $157.50   $157.50  
  Purchase #5 $88.89   6.369%   $94.5514   $94.55   $94.55   $94.60  
  Purchase #6 $185.25   8.520%   $201.0333   $201.03   $201.05   $201.00  
  Purchase #7 $182.68   8.852%   $198.8508   $198.85   $198.85   $198.90  
  7 purchase totals = $1,008.50       $1,110.9649   $1,110.96   $1,110.95   $1,111.00