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 $22.66   8.562%   $24.6001   $24.60   $24.60   $24.60  
  Purchase #2 $80.51   7.632%   $86.6545   $86.65   $86.65   $86.70  
  Purchase #3 $178.53   12.797%   $201.3765   $201.38   $201.40   $201.40  
  Purchase #4 $194.73   11.435%   $216.9974   $217.00   $217.00   $217.00  
  Purchase #5 $193.41   9.348%   $211.49   $211.49   $211.50   $211.50  
  Purchase #6 $100.97   12.783%   $113.877   $113.88   $113.90   $113.90  
  Purchase #7 $187.33   6.358%   $199.2404   $199.24   $199.25   $199.20  
  7 purchase totals = $958.14       $1,054.2359   $1,054.24   $1,054.30   $1,054.30