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 $214.29   5.338%   $225.7288   $225.73   $225.75   $225.70  
  Purchase #2 $130.71   11.470%   $145.7024   $145.70   $145.70   $145.70  
  Purchase #3 $248.73   3.153%   $256.5725   $256.57   $256.55   $256.60  
  Purchase #4 $142.45   9.353%   $155.7733   $155.77   $155.75   $155.80  
  Purchase #5 $118.38   11.457%   $131.9428   $131.94   $131.95   $131.90  
  Purchase #6 $76.84   9.128%   $83.854   $83.85   $83.85   $83.90  
  Purchase #7 $187.66   3.479%   $194.1887   $194.19   $194.20   $194.20  
  7 purchase totals = $1,119.06       $1,193.7625   $1,193.75   $1,193.75   $1,193.80