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 $87.67   5.791%   $92.747   $92.75   $92.75   $92.70  
  Purchase #2 $110.76   5.347%   $116.6823   $116.68   $116.70   $116.70  
  Purchase #3 $237.95   4.481%   $248.6125   $248.61   $248.60   $248.60  
  Purchase #4 $16.64   4.171%   $17.3341   $17.33   $17.35   $17.30  
  Purchase #5 $147.76   7.513%   $158.8612   $158.86   $158.85   $158.90  
  Purchase #6 $96.36   12.794%   $108.6883   $108.69   $108.70   $108.70  
  Purchase #7 $208.25   6.736%   $222.2777   $222.28   $222.30   $222.30  
  7 purchase totals = $905.39       $965.2031   $965.20   $965.25   $965.20