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 $184.43   10.573%   $203.9298   $203.93   $203.95   $203.90  
  Purchase #2 $246.48   8.138%   $266.5385   $266.54   $266.55   $266.50  
  Purchase #3 $196.75   4.217%   $205.0469   $205.05   $205.05   $205.00  
  Purchase #4 $51.92   4.770%   $54.3966   $54.40   $54.40   $54.40  
  Purchase #5 $10.50   4.489%   $10.9713   $10.97   $10.95   $11.00  
  Purchase #6 $168.96   8.262%   $182.9195   $182.92   $182.90   $182.90  
  Purchase #7 $236.91   3.585%   $245.4032   $245.40   $245.40   $245.40  
  7 purchase totals = $1,095.95       $1,169.2058   $1,169.21   $1,169.20   $1,169.10