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 $174.76   13.739%   $198.7703   $198.77   $198.75   $198.80  
  Purchase #2 $224.92   11.508%   $250.8038   $250.80   $250.80   $250.80  
  Purchase #3 $235.96   5.492%   $248.9189   $248.92   $248.90   $248.90  
  Purchase #4 $170.39   9.245%   $186.1426   $186.14   $186.15   $186.10  
  Purchase #5 $25.62   4.814%   $26.8533   $26.85   $26.85   $26.90  
  Purchase #6 $241.72   4.473%   $252.5321   $252.53   $252.55   $252.50  
  Purchase #7 $196.38   4.484%   $205.1857   $205.19   $205.20   $205.20  
  7 purchase totals = $1,269.75       $1,369.2067   $1,369.20   $1,369.20   $1,369.20