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 $56.84   9.424%   $62.1966   $62.20   $62.20   $62.20  
  Purchase #2 $39.79   10.590%   $44.0038   $44.00   $44.00   $44.00  
  Purchase #3 $139.70   11.403%   $155.63   $155.63   $155.65   $155.60  
  Purchase #4 $197.66   5.588%   $208.7052   $208.71   $208.70   $208.70  
  Purchase #5 $170.28   8.483%   $184.7249   $184.72   $184.70   $184.70  
  Purchase #6 $201.37   13.150%   $227.8502   $227.85   $227.85   $227.90  
  Purchase #7 $234.50   11.215%   $260.7992   $260.80   $260.80   $260.80  
  7 purchase totals = $1,040.14       $1,143.9099   $1,143.91   $1,143.90   $1,143.90