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 $86.98   11.482%   $96.967   $96.97   $96.95   $97.00  
  Purchase #2 $178.85   8.709%   $194.426   $194.43   $194.45   $194.40  
  Purchase #3 $102.62   9.383%   $112.2488   $112.25   $112.25   $112.20  
  Purchase #4 $219.92   4.685%   $230.2233   $230.22   $230.20   $230.20  
  Purchase #5 $134.93   9.709%   $148.0304   $148.03   $148.05   $148.00  
  Purchase #6 $235.40   8.386%   $255.1406   $255.14   $255.15   $255.10  
  Purchase #7 $11.28   3.636%   $11.6901   $11.69   $11.70   $11.70  
  7 purchase totals = $969.98       $1,048.7262   $1,048.73   $1,048.75   $1,048.60