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 $118.82   4.347%   $123.9851   $123.99   $124.00   $124.00  
  Purchase #2 $177.91   9.778%   $195.306   $195.31   $195.30   $195.30  
  Purchase #3 $72.37   13.261%   $81.967   $81.97   $81.95   $82.00  
  Purchase #4 $190.27   4.191%   $198.2442   $198.24   $198.25   $198.20  
  Purchase #5 $71.58   11.469%   $79.7895   $79.79   $79.80   $79.80  
  Purchase #6 $148.67   8.187%   $160.8416   $160.84   $160.85   $160.80  
  Purchase #7 $102.86   8.806%   $111.9179   $111.92   $111.90   $111.90  
  7 purchase totals = $882.48       $952.0513   $952.06   $952.05   $952.00