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 $176.71   10.869%   $195.9166   $195.92   $195.90   $195.90  
  Purchase #2 $230.58   10.296%   $254.3205   $254.32   $254.30   $254.30  
  Purchase #3 $95.30   11.329%   $106.0965   $106.10   $106.10   $106.10  
  Purchase #4 $141.56   13.516%   $160.6932   $160.69   $160.70   $160.70  
  Purchase #5 $127.33   11.517%   $141.9946   $141.99   $142.00   $142.00  
  Purchase #6 $227.67   5.606%   $240.4332   $240.43   $240.45   $240.40  
  Purchase #7 $126.70   4.768%   $132.7411   $132.74   $132.75   $132.70  
  7 purchase totals = $1,125.85       $1,232.1957   $1,232.19   $1,232.20   $1,232.10