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 $177.47   13.673%   $201.7355   $201.74   $201.75   $201.70  
  Purchase #2 $63.78   8.647%   $69.2951   $69.30   $69.30   $69.30  
  Purchase #3 $104.71   5.648%   $110.624   $110.62   $110.60   $110.60  
  Purchase #4 $244.91   12.537%   $275.6144   $275.61   $275.60   $275.60  
  Purchase #5 $197.72   5.175%   $207.952   $207.95   $207.95   $208.00  
  Purchase #6 $167.94   7.382%   $180.3373   $180.34   $180.35   $180.30  
  Purchase #7 $127.74   5.531%   $134.8053   $134.81   $134.80   $134.80  
  7 purchase totals = $1,084.27       $1,180.3636   $1,180.37   $1,180.35   $1,180.30