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 $49.72   12.727%   $56.0479   $56.05   $56.05   $56.00  
  Purchase #2 $226.59   6.384%   $241.0555   $241.06   $241.05   $241.10  
  Purchase #3 $60.80   13.472%   $68.991   $68.99   $69.00   $69.00  
  Purchase #4 $224.42   6.568%   $239.1599   $239.16   $239.15   $239.20  
  Purchase #5 $204.53   3.743%   $212.1856   $212.19   $212.20   $212.20  
  Purchase #6 $161.95   6.546%   $172.5512   $172.55   $172.55   $172.60  
  Purchase #7 $32.73   8.490%   $35.5088   $35.51   $35.50   $35.50  
  7 purchase totals = $960.74       $1,025.4999   $1,025.51   $1,025.50   $1,025.60