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 $96.70   9.730%   $106.1089   $106.11   $106.10   $106.10  
  Purchase #2 $196.47   4.454%   $205.2208   $205.22   $205.20   $205.20  
  Purchase #3 $118.42   11.120%   $131.5883   $131.59   $131.60   $131.60  
  Purchase #4 $24.96   8.464%   $27.0726   $27.07   $27.05   $27.10  
  Purchase #5 $239.49   13.799%   $272.5372   $272.54   $272.55   $272.50  
  Purchase #6 $198.97   9.144%   $217.1638   $217.16   $217.15   $217.20  
  Purchase #7 $109.86   5.870%   $116.3088   $116.31   $116.30   $116.30  
  7 purchase totals = $984.87       $1,076.0004   $1,076.00   $1,075.95   $1,076.00