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 $191.64   7.295%   $205.6201   $205.62   $205.60   $205.60  
  Purchase #2 $223.73   8.847%   $243.5234   $243.52   $243.50   $243.50  
  Purchase #3 $199.86   13.545%   $226.931   $226.93   $226.95   $226.90  
  Purchase #4 $225.67   6.685%   $240.756   $240.76   $240.75   $240.80  
  Purchase #5 $46.81   9.226%   $51.1287   $51.13   $51.15   $51.10  
  Purchase #6 $104.75   10.229%   $115.4649   $115.46   $115.45   $115.50  
  Purchase #7 $74.66   7.819%   $80.4977   $80.50   $80.50   $80.50  
  7 purchase totals = $1,067.12       $1,163.9218   $1,163.92   $1,163.90   $1,163.90