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 $186.60   5.404%   $196.6839   $196.68   $196.70   $196.70  
  Purchase #2 $65.52   5.797%   $69.3182   $69.32   $69.30   $69.30  
  Purchase #3 $118.82   3.394%   $122.8528   $122.85   $122.85   $122.90  
  Purchase #4 $197.53   6.441%   $210.2529   $210.25   $210.25   $210.30  
  Purchase #5 $198.70   6.530%   $211.6751   $211.68   $211.70   $211.70  
  Purchase #6 $57.32   3.454%   $59.2998   $59.30   $59.30   $59.30  
  Purchase #7 $17.74   5.112%   $18.6469   $18.65   $18.65   $18.60  
  7 purchase totals = $842.23       $888.7296   $888.73   $888.75   $888.80