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 $118.66   6.240%   $126.0644   $126.06   $126.05   $126.10  
  Purchase #2 $76.49   8.667%   $83.1194   $83.12   $83.10   $83.10  
  Purchase #3 $190.49   8.421%   $206.5312   $206.53   $206.55   $206.50  
  Purchase #4 $93.82   8.355%   $101.6587   $101.66   $101.65   $101.70  
  Purchase #5 $152.60   5.321%   $160.7198   $160.72   $160.70   $160.70  
  Purchase #6 $174.34   7.399%   $187.2394   $187.24   $187.25   $187.20  
  Purchase #7 $194.62   7.188%   $208.6093   $208.61   $208.60   $208.60  
  7 purchase totals = $1,001.02       $1,073.9422   $1,073.94   $1,073.90   $1,073.90