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 $91.73   4.652%   $95.9973   $96.00   $96.00   $96.00  
  Purchase #2 $51.78   3.684%   $53.6876   $53.69   $53.70   $53.70  
  Purchase #3 $170.36   5.288%   $179.3686   $179.37   $179.35   $179.40  
  Purchase #4 $226.73   4.762%   $237.5269   $237.53   $237.55   $237.50  
  Purchase #5 $50.81   13.111%   $57.4717   $57.47   $57.45   $57.50  
  Purchase #6 $158.92   3.692%   $164.7873   $164.79   $164.80   $164.80  
  Purchase #7 $197.32   10.314%   $217.6716   $217.67   $217.65   $217.70  
  7 purchase totals = $947.65       $1,006.5110   $1,006.52   $1,006.50   $1,006.60