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 $31.39   13.573%   $35.6506   $35.65   $35.65   $35.70  
  Purchase #2 $115.67   11.477%   $128.9454   $128.95   $128.95   $128.90  
  Purchase #3 $209.89   6.405%   $223.3335   $223.33   $223.35   $223.30  
  Purchase #4 $246.92   12.240%   $277.143   $277.14   $277.15   $277.10  
  Purchase #5 $44.88   3.339%   $46.3785   $46.38   $46.40   $46.40  
  Purchase #6 $173.52   11.832%   $194.0509   $194.05   $194.05   $194.10  
  Purchase #7 $97.32   11.706%   $108.7123   $108.71   $108.70   $108.70  
  7 purchase totals = $919.59       $1,014.2142   $1,014.21   $1,014.25   $1,014.20