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 $125.84   6.486%   $134.002   $134.00   $134.00   $134.00  
  Purchase #2 $114.60   4.548%   $119.812   $119.81   $119.80   $119.80  
  Purchase #3 $10.58   4.521%   $11.0583   $11.06   $11.05   $11.10  
  Purchase #4 $18.26   8.751%   $19.8579   $19.86   $19.85   $19.90  
  Purchase #5 $60.91   11.264%   $67.7709   $67.77   $67.75   $67.80  
  Purchase #6 $85.37   11.279%   $94.9989   $95.00   $95.00   $95.00  
  Purchase #7 $114.44   10.253%   $126.1735   $126.17   $126.15   $126.20  
  7 purchase totals = $530.00       $573.6735   $573.67   $573.60   $573.80