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 $244.47   8.823%   $266.0396   $266.04   $266.05   $266.00  
  Purchase #2 $41.43   5.396%   $43.6656   $43.67   $43.65   $43.70  
  Purchase #3 $237.36   11.361%   $264.3265   $264.33   $264.35   $264.30  
  Purchase #4 $99.59   10.476%   $110.023   $110.02   $110.00   $110.00  
  Purchase #5 $29.92   10.220%   $32.9778   $32.98   $33.00   $33.00  
  Purchase #6 $106.49   7.738%   $114.7302   $114.73   $114.75   $114.70  
  Purchase #7 $201.86   4.648%   $211.2425   $211.24   $211.25   $211.20  
  7 purchase totals = $961.12       $1,043.0052   $1,043.01   $1,043.05   $1,042.90