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 $31.90   9.640%   $34.9752   $34.98   $35.00   $35.00  
  Purchase #2 $236.45   12.161%   $265.2047   $265.20   $265.20   $265.20  
  Purchase #3 $216.49   3.105%   $223.212   $223.21   $223.20   $223.20  
  Purchase #4 $239.28   3.778%   $248.32   $248.32   $248.30   $248.30  
  Purchase #5 $26.44   12.293%   $29.6903   $29.69   $29.70   $29.70  
  Purchase #6 $155.40   12.316%   $174.5391   $174.54   $174.55   $174.50  
  Purchase #7 $68.88   12.870%   $77.7449   $77.74   $77.75   $77.70  
  7 purchase totals = $974.84       $1,053.6862   $1,053.68   $1,053.70   $1,053.60