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 $53.75   6.502%   $57.2448   $57.24   $57.25   $57.20  
  Purchase #2 $166.58   11.721%   $186.1048   $186.10   $186.10   $186.10  
  Purchase #3 $199.27   6.526%   $212.2744   $212.27   $212.25   $212.30  
  Purchase #4 $87.70   3.160%   $90.4713   $90.47   $90.45   $90.50  
  Purchase #5 $157.32   11.874%   $176.0002   $176.00   $176.00   $176.00  
  Purchase #6 $78.53   8.401%   $85.1273   $85.13   $85.15   $85.10  
  Purchase #7 $185.62   11.414%   $206.8067   $206.81   $206.80   $206.80  
  7 purchase totals = $928.77       $1,014.0295   $1,014.02   $1,014.00   $1,014.00