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 $59.69   7.116%   $63.9375   $63.94   $63.95   $63.90  
  Purchase #2 $217.77   3.834%   $226.1193   $226.12   $226.10   $226.10  
  Purchase #3 $112.30   9.365%   $122.8169   $122.82   $122.80   $122.80  
  Purchase #4 $16.74   8.596%   $18.179   $18.18   $18.20   $18.20  
  Purchase #5 $21.55   3.113%   $22.2209   $22.22   $22.20   $22.20  
  Purchase #6 $224.61   7.853%   $242.2486   $242.25   $242.25   $242.20  
  Purchase #7 $52.29   13.205%   $59.1949   $59.19   $59.20   $59.20  
  7 purchase totals = $704.95       $754.7171   $754.72   $754.70   $754.60