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 $87.32   9.838%   $95.9105   $95.91   $95.90   $95.90  
  Purchase #2 $187.95   5.296%   $197.9038   $197.90   $197.90   $197.90  
  Purchase #3 $143.28   8.687%   $155.7267   $155.73   $155.75   $155.70  
  Purchase #4 $67.70   11.461%   $75.4591   $75.46   $75.45   $75.50  
  Purchase #5 $148.73   8.844%   $161.8837   $161.88   $161.90   $161.90  
  Purchase #6 $165.42   10.118%   $182.1572   $182.16   $182.15   $182.20  
  Purchase #7 $173.33   7.320%   $186.0178   $186.02   $186.00   $186.00  
  7 purchase totals = $973.73       $1,055.0588   $1,055.06   $1,055.05   $1,055.10