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 $118.88   6.203%   $126.2541   $126.25   $126.25   $126.30  
  Purchase #2 $112.62   8.601%   $122.3064   $122.31   $122.30   $122.30  
  Purchase #3 $63.25   9.481%   $69.2467   $69.25   $69.25   $69.20  
  Purchase #4 $249.30   5.290%   $262.488   $262.49   $262.50   $262.50  
  Purchase #5 $233.35   13.500%   $264.8523   $264.85   $264.85   $264.90  
  Purchase #6 $244.60   7.214%   $262.2454   $262.25   $262.25   $262.20  
  Purchase #7 $232.46   10.560%   $257.0078   $257.01   $257.00   $257.00  
  7 purchase totals = $1,254.46       $1,364.4007   $1,364.41   $1,364.40   $1,364.40