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 $94.56   3.853%   $98.2034   $98.20   $98.20   $98.20  
  Purchase #2 $21.36   13.481%   $24.2395   $24.24   $24.25   $24.20  
  Purchase #3 $198.65   5.418%   $209.4129   $209.41   $209.40   $209.40  
  Purchase #4 $39.80   4.634%   $41.6443   $41.64   $41.65   $41.60  
  Purchase #5 $247.52   7.167%   $265.2598   $265.26   $265.25   $265.30  
  Purchase #6 $223.70   13.380%   $253.6311   $253.63   $253.65   $253.60  
  Purchase #7 $215.87   11.704%   $241.1354   $241.14   $241.15   $241.10  
  7 purchase totals = $1,041.46       $1,133.5264   $1,133.52   $1,133.55   $1,133.40