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 $216.44   7.458%   $232.5821   $232.58   $232.60   $232.60  
  Purchase #2 $244.25   12.855%   $275.6483   $275.65   $275.65   $275.60  
  Purchase #3 $234.55   12.873%   $264.7436   $264.74   $264.75   $264.70  
  Purchase #4 $99.59   7.571%   $107.13   $107.13   $107.15   $107.10  
  Purchase #5 $246.65   13.591%   $280.1722   $280.17   $280.15   $280.20  
  Purchase #6 $241.38   10.480%   $266.6766   $266.68   $266.70   $266.70  
  Purchase #7 $182.76   12.305%   $205.2486   $205.25   $205.25   $205.20  
  7 purchase totals = $1,465.62       $1,632.2014   $1,632.20   $1,632.25   $1,632.10