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 $85.81   11.273%   $95.4834   $95.48   $95.50   $95.50  
  Purchase #2 $181.30   11.226%   $201.6527   $201.65   $201.65   $201.70  
  Purchase #3 $249.66   3.174%   $257.5842   $257.58   $257.60   $257.60  
  Purchase #4 $212.51   7.674%   $228.818   $228.82   $228.80   $228.80  
  Purchase #5 $101.79   13.746%   $115.7821   $115.78   $115.80   $115.80  
  Purchase #6 $176.65   8.531%   $191.72   $191.72   $191.70   $191.70  
  Purchase #7 $192.72   11.264%   $214.428   $214.43   $214.45   $214.40  
  7 purchase totals = $1,200.44       $1,305.4684   $1,305.46   $1,305.50   $1,305.50