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 $188.61   6.575%   $201.0111   $201.01   $201.00   $201.00  
  Purchase #2 $115.40   7.327%   $123.8554   $123.86   $123.85   $123.90  
  Purchase #3 $148.88   13.128%   $168.425   $168.43   $168.45   $168.40  
  Purchase #4 $207.41   11.166%   $230.5694   $230.57   $230.55   $230.60  
  Purchase #5 $33.32   8.555%   $36.1705   $36.17   $36.15   $36.20  
  Purchase #6 $96.50   7.872%   $104.0965   $104.10   $104.10   $104.10  
  Purchase #7 $188.41   11.790%   $210.6235   $210.62   $210.60   $210.60  
  7 purchase totals = $978.53       $1,074.7514   $1,074.76   $1,074.70   $1,074.80