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 $214.89   10.577%   $237.6189   $237.62   $237.60   $237.60  
  Purchase #2 $7.50   3.306%   $7.748   $7.75   $7.75   $7.70  
  Purchase #3 $126.48   3.328%   $130.6893   $130.69   $130.70   $130.70  
  Purchase #4 $203.29   7.434%   $218.4026   $218.40   $218.40   $218.40  
  Purchase #5 $49.69   7.436%   $53.3849   $53.38   $53.40   $53.40  
  Purchase #6 $189.94   5.103%   $199.6326   $199.63   $199.65   $199.60  
  Purchase #7 $165.70   5.615%   $175.0041   $175.00   $175.00   $175.00  
  7 purchase totals = $957.49       $1,022.4804   $1,022.47   $1,022.50   $1,022.40