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 $59.61   10.214%   $65.6986   $65.70   $65.70   $65.70  
  Purchase #2 $104.91   12.635%   $118.1654   $118.17   $118.15   $118.20  
  Purchase #3 $230.41   8.616%   $250.2621   $250.26   $250.25   $250.30  
  Purchase #4 $189.93   13.845%   $216.2258   $216.23   $216.25   $216.20  
  Purchase #5 $149.37   5.297%   $157.2821   $157.28   $157.30   $157.30  
  Purchase #6 $95.82   9.283%   $104.715   $104.72   $104.70   $104.70  
  Purchase #7 $227.97   5.608%   $240.7546   $240.75   $240.75   $240.80  
  7 purchase totals = $1,058.02       $1,153.1036   $1,153.11   $1,153.10   $1,153.20