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 $146.88   3.829%   $152.504   $152.50   $152.50   $152.50  
  Purchase #2 $218.84   6.258%   $232.535   $232.54   $232.55   $232.50  
  Purchase #3 $245.81   5.711%   $259.8482   $259.85   $259.85   $259.80  
  Purchase #4 $122.82   12.669%   $138.3801   $138.38   $138.40   $138.40  
  Purchase #5 $183.93   11.325%   $204.7601   $204.76   $204.75   $204.80  
  Purchase #6 $142.97   3.328%   $147.728   $147.73   $147.75   $147.70  
  Purchase #7 $53.30   11.278%   $59.3112   $59.31   $59.30   $59.30  
  7 purchase totals = $1,114.55       $1,195.0666   $1,195.07   $1,195.10   $1,195.00