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 $24.25   10.495%   $26.795   $26.80   $26.80   $26.80  
  Purchase #2 $197.33   3.518%   $204.2721   $204.27   $204.25   $204.30  
  Purchase #3 $165.64   10.146%   $182.4458   $182.45   $182.45   $182.40  
  Purchase #4 $22.82   5.759%   $24.1342   $24.13   $24.15   $24.10  
  Purchase #5 $212.89   9.486%   $233.0847   $233.08   $233.10   $233.10  
  Purchase #6 $86.88   9.496%   $95.1301   $95.13   $95.15   $95.10  
  Purchase #7 $176.70   10.499%   $195.2517   $195.25   $195.25   $195.30  
  7 purchase totals = $886.51       $961.1136   $961.11   $961.15   $961.10