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 $85.71   10.787%   $94.9555   $94.96   $94.95   $95.00  
  Purchase #2 $147.73   10.122%   $162.6832   $162.68   $162.70   $162.70  
  Purchase #3 $203.68   13.834%   $231.8571   $231.86   $231.85   $231.90  
  Purchase #4 $17.68   6.693%   $18.8633   $18.86   $18.85   $18.90  
  Purchase #5 $22.56   5.116%   $23.7142   $23.71   $23.70   $23.70  
  Purchase #6 $161.73   3.611%   $167.5701   $167.57   $167.55   $167.60  
  Purchase #7 $68.31   4.602%   $71.4536   $71.45   $71.45   $71.50  
  7 purchase totals = $707.40       $771.0970   $771.09   $771.05   $771.30