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 $144.67   7.554%   $155.5984   $155.60   $155.60   $155.60  
  Purchase #2 $98.66   3.752%   $102.3617   $102.36   $102.35   $102.40  
  Purchase #3 $186.49   4.587%   $195.0443   $195.04   $195.05   $195.00  
  Purchase #4 $156.72   4.482%   $163.7442   $163.74   $163.75   $163.70  
  Purchase #5 $10.47   8.512%   $11.3612   $11.36   $11.35   $11.40  
  Purchase #6 $198.84   3.513%   $205.8252   $205.83   $205.85   $205.80  
  Purchase #7 $167.37   7.801%   $180.4265   $180.43   $180.45   $180.40  
  7 purchase totals = $963.22       $1,014.3615   $1,014.36   $1,014.40   $1,014.30