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 $106.36   7.292%   $114.1158   $114.12   $114.10   $114.10  
  Purchase #2 $229.61   5.243%   $241.6485   $241.65   $241.65   $241.60  
  Purchase #3 $207.60   12.203%   $232.9334   $232.93   $232.95   $232.90  
  Purchase #4 $236.45   4.264%   $246.5322   $246.53   $246.55   $246.50  
  Purchase #5 $151.80   10.529%   $167.783   $167.78   $167.80   $167.80  
  Purchase #6 $157.82   13.742%   $179.5076   $179.51   $179.50   $179.50  
  Purchase #7 $133.71   4.784%   $140.1067   $140.11   $140.10   $140.10  
  7 purchase totals = $1,223.35       $1,322.6272   $1,322.63   $1,322.65   $1,322.50