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 $211.64   10.417%   $233.6865   $233.69   $233.70   $233.70  
  Purchase #2 $32.72   5.825%   $34.6259   $34.63   $34.65   $34.60  
  Purchase #3 $86.80   8.342%   $94.0409   $94.04   $94.05   $94.00  
  Purchase #4 $182.93   7.831%   $197.2552   $197.26   $197.25   $197.30  
  Purchase #5 $237.34   3.342%   $245.2719   $245.27   $245.25   $245.30  
  Purchase #6 $171.69   8.813%   $186.821   $186.82   $186.80   $186.80  
  Purchase #7 $47.99   4.555%   $50.1759   $50.18   $50.20   $50.20  
  7 purchase totals = $971.11       $1,041.8773   $1,041.89   $1,041.90   $1,041.90