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 $24.72   5.323%   $26.0358   $26.04   $26.05   $26.00  
  Purchase #2 $152.96   8.612%   $166.1329   $166.13   $166.15   $166.10  
  Purchase #3 $98.67   12.323%   $110.8291   $110.83   $110.85   $110.80  
  Purchase #4 $159.99   5.554%   $168.8758   $168.88   $168.90   $168.90  
  Purchase #5 $107.69   13.379%   $122.0978   $122.10   $122.10   $122.10  
  Purchase #6 $147.74   7.514%   $158.8412   $158.84   $158.85   $158.80  
  Purchase #7 $117.81   5.160%   $123.889   $123.89   $123.90   $123.90  
  7 purchase totals = $809.58       $876.7016   $876.71   $876.80   $876.60