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 $162.35   7.261%   $174.1382   $174.14   $174.15   $174.10  
  Purchase #2 $180.89   13.440%   $205.2016   $205.20   $205.20   $205.20  
  Purchase #3 $195.72   9.649%   $214.605   $214.61   $214.60   $214.60  
  Purchase #4 $101.34   6.510%   $107.9372   $107.94   $107.95   $107.90  
  Purchase #5 $248.66   7.474%   $267.2448   $267.24   $267.25   $267.20  
  Purchase #6 $92.94   10.590%   $102.7823   $102.78   $102.80   $102.80  
  Purchase #7 $122.48   3.632%   $126.9285   $126.93   $126.95   $126.90  
  7 purchase totals = $1,104.38       $1,198.8376   $1,198.84   $1,198.90   $1,198.70