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 $69.42   7.573%   $74.6772   $74.68   $74.70   $74.70  
  Purchase #2 $229.41   13.360%   $260.0592   $260.06   $260.05   $260.10  
  Purchase #3 $213.88   4.324%   $223.1282   $223.13   $223.15   $223.10  
  Purchase #4 $89.66   9.476%   $98.1562   $98.16   $98.15   $98.20  
  Purchase #5 $135.57   6.130%   $143.8804   $143.88   $143.90   $143.90  
  Purchase #6 $167.37   5.733%   $176.9653   $176.97   $176.95   $177.00  
  Purchase #7 $172.94   5.862%   $183.0777   $183.08   $183.10   $183.10  
  7 purchase totals = $1,078.25       $1,159.9442   $1,159.96   $1,160.00   $1,160.10