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 $177.28   5.874%   $187.6934   $187.69   $187.70   $187.70  
  Purchase #2 $53.53   9.403%   $58.5634   $58.56   $58.55   $58.60  
  Purchase #3 $250.67   9.448%   $274.3533   $274.35   $274.35   $274.40  
  Purchase #4 $39.35   3.187%   $40.6041   $40.60   $40.60   $40.60  
  Purchase #5 $73.94   5.410%   $77.9402   $77.94   $77.95   $77.90  
  Purchase #6 $92.95   6.252%   $98.7612   $98.76   $98.75   $98.80  
  Purchase #7 $246.47   12.334%   $276.8696   $276.87   $276.85   $276.90  
  7 purchase totals = $934.19       $1,014.7852   $1,014.77   $1,014.75   $1,014.90