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 $153.79   5.489%   $162.2315   $162.23   $162.25   $162.20  
  Purchase #2 $51.75   11.435%   $57.6676   $57.67   $57.65   $57.70  
  Purchase #3 $116.57   6.614%   $124.2799   $124.28   $124.30   $124.30  
  Purchase #4 $192.71   4.477%   $201.3376   $201.34   $201.35   $201.30  
  Purchase #5 $60.34   4.840%   $63.2605   $63.26   $63.25   $63.30  
  Purchase #6 $156.94   5.576%   $165.691   $165.69   $165.70   $165.70  
  Purchase #7 $207.31   11.495%   $231.1403   $231.14   $231.15   $231.10  
  7 purchase totals = $939.41       $1,005.6084   $1,005.61   $1,005.65   $1,005.60