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 $53.56   10.264%   $59.0574   $59.06   $59.05   $59.10  
  Purchase #2 $247.42   8.368%   $268.1241   $268.12   $268.10   $268.10  
  Purchase #3 $127.49   6.162%   $135.3459   $135.35   $135.35   $135.30  
  Purchase #4 $82.29   12.416%   $92.5071   $92.51   $92.50   $92.50  
  Purchase #5 $124.27   11.558%   $138.6331   $138.63   $138.65   $138.60  
  Purchase #6 $237.55   13.395%   $269.3698   $269.37   $269.35   $269.40  
  Purchase #7 $219.66   10.192%   $242.0477   $242.05   $242.05   $242.00  
  7 purchase totals = $1,092.24       $1,205.0851   $1,205.09   $1,205.05   $1,205.00