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 $23.81   9.342%   $26.0343   $26.03   $26.05   $26.00  
  Purchase #2 $147.32   3.499%   $152.4747   $152.47   $152.45   $152.50  
  Purchase #3 $239.49   11.369%   $266.7176   $266.72   $266.70   $266.70  
  Purchase #4 $185.39   4.865%   $194.4092   $194.41   $194.40   $194.40  
  Purchase #5 $232.75   6.754%   $248.4699   $248.47   $248.45   $248.50  
  Purchase #6 $142.53   13.417%   $161.6533   $161.65   $161.65   $161.70  
  Purchase #7 $25.52   3.746%   $26.476   $26.48   $26.50   $26.50  
  7 purchase totals = $996.81       $1,076.2350   $1,076.23   $1,076.20   $1,076.30