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 $61.87   5.754%   $65.43   $65.43   $65.45   $65.40  
  Purchase #2 $143.44   4.228%   $149.5046   $149.50   $149.50   $149.50  
  Purchase #3 $172.50   7.510%   $185.4548   $185.45   $185.45   $185.50  
  Purchase #4 $74.42   5.811%   $78.7445   $78.74   $78.75   $78.70  
  Purchase #5 $214.49   4.752%   $224.6826   $224.68   $224.70   $224.70  
  Purchase #6 $42.78   11.108%   $47.532   $47.53   $47.55   $47.50  
  Purchase #7 $202.45   4.823%   $212.2142   $212.21   $212.20   $212.20  
  7 purchase totals = $911.95       $963.5627   $963.54   $963.60   $963.50