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 $160.83   9.226%   $175.6682   $175.67   $175.65   $175.70  
  Purchase #2 $52.89   11.798%   $59.13   $59.13   $59.15   $59.10  
  Purchase #3 $24.53   7.194%   $26.2947   $26.29   $26.30   $26.30  
  Purchase #4 $237.91   8.141%   $257.2783   $257.28   $257.30   $257.30  
  Purchase #5 $216.69   10.192%   $238.775   $238.78   $238.80   $238.80  
  Purchase #6 $211.37   3.184%   $218.1   $218.10   $218.10   $218.10  
  Purchase #7 $111.65   9.497%   $122.2534   $122.25   $122.25   $122.30  
  7 purchase totals = $1,015.87       $1,097.4996   $1,097.50   $1,097.55   $1,097.60