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 $204.48   11.842%   $228.6945   $228.69   $228.70   $228.70  
  Purchase #2 $63.87   8.867%   $69.5334   $69.53   $69.55   $69.50  
  Purchase #3 $232.74   8.264%   $251.9736   $251.97   $251.95   $252.00  
  Purchase #4 $97.66   8.495%   $105.9562   $105.96   $105.95   $106.00  
  Purchase #5 $124.78   7.762%   $134.4654   $134.47   $134.45   $134.50  
  Purchase #6 $150.33   9.853%   $165.142   $165.14   $165.15   $165.10  
  Purchase #7 $190.48   11.394%   $212.1833   $212.18   $212.20   $212.20  
  7 purchase totals = $1,064.34       $1,167.9484   $1,167.94   $1,167.95   $1,168.00