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 $187.61   3.212%   $193.636   $193.64   $193.65   $193.60  
  Purchase #2 $193.28   10.392%   $213.3657   $213.37   $213.35   $213.40  
  Purchase #3 $84.63   12.208%   $94.9616   $94.96   $94.95   $95.00  
  Purchase #4 $166.30   8.190%   $179.92   $179.92   $179.90   $179.90  
  Purchase #5 $130.74   6.854%   $139.7009   $139.70   $139.70   $139.70  
  Purchase #6 $210.54   13.586%   $239.144   $239.14   $239.15   $239.10  
  Purchase #7 $100.63   8.530%   $109.2137   $109.21   $109.20   $109.20  
  7 purchase totals = $1,073.73       $1,169.9419   $1,169.94   $1,169.90   $1,169.90