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 $62.69   8.389%   $67.9491   $67.95   $67.95   $67.90  
  Purchase #2 $83.28   12.727%   $93.879   $93.88   $93.90   $93.90  
  Purchase #3 $58.72   12.272%   $65.9261   $65.93   $65.95   $65.90  
  Purchase #4 $177.33   3.692%   $183.877   $183.88   $183.90   $183.90  
  Purchase #5 $179.57   7.374%   $192.8115   $192.81   $192.80   $192.80  
  Purchase #6 $56.42   5.764%   $59.672   $59.67   $59.65   $59.70  
  Purchase #7 $153.40   6.220%   $162.9415   $162.94   $162.95   $162.90  
  7 purchase totals = $771.41       $827.0562   $827.06   $827.10   $827.00