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 $184.75   9.545%   $202.3844   $202.38   $202.40   $202.40  
  Purchase #2 $59.70   13.126%   $67.5362   $67.54   $67.55   $67.50  
  Purchase #3 $42.60   5.504%   $44.9447   $44.94   $44.95   $44.90  
  Purchase #4 $227.76   9.770%   $250.0122   $250.01   $250.00   $250.00  
  Purchase #5 $176.34   10.271%   $194.4519   $194.45   $194.45   $194.50  
  Purchase #6 $49.86   9.176%   $54.4352   $54.44   $54.45   $54.40  
  Purchase #7 $191.84   4.751%   $200.9543   $200.95   $200.95   $201.00  
  7 purchase totals = $932.85       $1,014.7189   $1,014.71   $1,014.75   $1,014.70