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 $212.25   10.140%   $233.7722   $233.77   $233.75   $233.80  
  Purchase #2 $92.91   6.231%   $98.6992   $98.70   $98.70   $98.70  
  Purchase #3 $19.31   8.871%   $21.023   $21.02   $21.00   $21.00  
  Purchase #4 $177.86   11.437%   $198.2018   $198.20   $198.20   $198.20  
  Purchase #5 $210.95   11.180%   $234.5342   $234.53   $234.55   $234.50  
  Purchase #6 $60.28   4.368%   $62.913   $62.91   $62.90   $62.90  
  Purchase #7 $190.63   7.850%   $205.5945   $205.59   $205.60   $205.60  
  7 purchase totals = $964.19       $1,054.7379   $1,054.72   $1,054.70   $1,054.70