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 $248.33   5.794%   $262.7182   $262.72   $262.70   $262.70  
  Purchase #2 $228.66   4.392%   $238.7027   $238.70   $238.70   $238.70  
  Purchase #3 $61.31   12.383%   $68.902   $68.90   $68.90   $68.90  
  Purchase #4 $51.85   13.705%   $58.956   $58.96   $58.95   $59.00  
  Purchase #5 $198.59   12.400%   $223.2152   $223.22   $223.20   $223.20  
  Purchase #6 $165.29   5.384%   $174.1892   $174.19   $174.20   $174.20  
  Purchase #7 $153.51   8.553%   $166.6397   $166.64   $166.65   $166.60  
  7 purchase totals = $1,107.54       $1,193.3230   $1,193.33   $1,193.30   $1,193.30