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 $90.83   5.200%   $95.5532   $95.55   $95.55   $95.60  
  Purchase #2 $216.79   3.427%   $224.2194   $224.22   $224.20   $224.20  
  Purchase #3 $62.61   10.359%   $69.0958   $69.10   $69.10   $69.10  
  Purchase #4 $115.43   13.638%   $131.1723   $131.17   $131.15   $131.20  
  Purchase #5 $193.69   13.269%   $219.3907   $219.39   $219.40   $219.40  
  Purchase #6 $87.83   9.771%   $96.4119   $96.41   $96.40   $96.40  
  Purchase #7 $96.43   12.838%   $108.8097   $108.81   $108.80   $108.80  
  7 purchase totals = $863.61       $944.6530   $944.65   $944.60   $944.70