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 $37.46   7.257%   $40.1785   $40.18   $40.20   $40.20  
  Purchase #2 $47.71   11.693%   $53.2887   $53.29   $53.30   $53.30  
  Purchase #3 $70.79   7.511%   $76.107   $76.11   $76.10   $76.10  
  Purchase #4 $205.44   8.403%   $222.7031   $222.70   $222.70   $222.70  
  Purchase #5 $199.88   8.311%   $216.492   $216.49   $216.50   $216.50  
  Purchase #6 $190.46   11.796%   $212.9267   $212.93   $212.95   $212.90  
  Purchase #7 $177.76   8.432%   $192.7487   $192.75   $192.75   $192.70  
  7 purchase totals = $929.50       $1,014.4447   $1,014.45   $1,014.50   $1,014.40