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 $187.51   9.500%   $205.3235   $205.32   $205.30   $205.30  
  Purchase #2 $205.29   13.339%   $232.6736   $232.67   $232.65   $232.70  
  Purchase #3 $136.49   3.791%   $141.6643   $141.66   $141.65   $141.70  
  Purchase #4 $55.67   12.600%   $62.6844   $62.68   $62.70   $62.70  
  Purchase #5 $142.69   6.318%   $151.7052   $151.71   $151.70   $151.70  
  Purchase #6 $234.27   11.847%   $262.024   $262.02   $262.00   $262.00  
  Purchase #7 $147.47   3.299%   $152.335   $152.34   $152.35   $152.30  
  7 purchase totals = $1,109.39       $1,208.4100   $1,208.40   $1,208.35   $1,208.40