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 $86.50   10.840%   $95.8766   $95.88   $95.90   $95.90  
  Purchase #2 $10.73   3.229%   $11.0765   $11.08   $11.10   $11.10  
  Purchase #3 $125.83   5.438%   $132.6726   $132.67   $132.65   $132.70  
  Purchase #4 $178.48   6.839%   $190.6862   $190.69   $190.70   $190.70  
  Purchase #5 $230.46   9.360%   $252.0311   $252.03   $252.05   $252.00  
  Purchase #6 $202.56   10.294%   $223.4115   $223.41   $223.40   $223.40  
  Purchase #7 $205.56   9.737%   $225.5754   $225.58   $225.60   $225.60  
  7 purchase totals = $1,040.12       $1,131.3299   $1,131.34   $1,131.40   $1,131.40