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 $32.80   6.605%   $34.9664   $34.97   $34.95   $35.00  
  Purchase #2 $192.47   13.120%   $217.7221   $217.72   $217.70   $217.70  
  Purchase #3 $67.55   3.394%   $69.8426   $69.84   $69.85   $69.80  
  Purchase #4 $55.77   9.555%   $61.0988   $61.10   $61.10   $61.10  
  Purchase #5 $235.79   5.267%   $248.2091   $248.21   $248.20   $248.20  
  Purchase #6 $234.62   12.692%   $264.398   $264.40   $264.40   $264.40  
  Purchase #7 $169.98   11.135%   $188.9073   $188.91   $188.90   $188.90  
  7 purchase totals = $988.98       $1,085.1443   $1,085.15   $1,085.10   $1,085.10