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 $95.66   5.328%   $100.7568   $100.76   $100.75   $100.80  
  Purchase #2 $206.49   5.481%   $217.8077   $217.81   $217.80   $217.80  
  Purchase #3 $53.68   4.452%   $56.0698   $56.07   $56.05   $56.10  
  Purchase #4 $222.65   13.865%   $253.5204   $253.52   $253.50   $253.50  
  Purchase #5 $192.98   4.838%   $202.3164   $202.32   $202.30   $202.30  
  Purchase #6 $138.33   8.353%   $149.8847   $149.88   $149.90   $149.90  
  Purchase #7 $76.47   5.202%   $80.448   $80.45   $80.45   $80.40  
  7 purchase totals = $986.26       $1,060.8038   $1,060.81   $1,060.75   $1,060.80