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 $167.81   5.259%   $176.6351   $176.64   $176.65   $176.60  
  Purchase #2 $194.39   6.285%   $206.6074   $206.61   $206.60   $206.60  
  Purchase #3 $230.86   5.473%   $243.495   $243.50   $243.50   $243.50  
  Purchase #4 $46.72   10.717%   $51.727   $51.73   $51.75   $51.70  
  Purchase #5 $245.43   8.296%   $265.7909   $265.79   $265.80   $265.80  
  Purchase #6 $240.28   11.868%   $268.7964   $268.80   $268.80   $268.80  
  Purchase #7 $51.67   8.417%   $56.0191   $56.02   $56.00   $56.00  
  7 purchase totals = $1,177.16       $1,269.0709   $1,269.09   $1,269.10   $1,269.00