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 $177.45   13.559%   $201.5104   $201.51   $201.50   $201.50  
  Purchase #2 $41.41   8.255%   $44.8284   $44.83   $44.85   $44.80  
  Purchase #3 $172.77   13.802%   $196.6157   $196.62   $196.60   $196.60  
  Purchase #4 $147.33   6.589%   $157.0376   $157.04   $157.05   $157.00  
  Purchase #5 $68.89   8.420%   $74.6905   $74.69   $74.70   $74.70  
  Purchase #6 $224.81   11.567%   $250.8138   $250.81   $250.80   $250.80  
  Purchase #7 $93.90   13.651%   $106.7183   $106.72   $106.70   $106.70  
  7 purchase totals = $926.56       $1,032.2147   $1,032.22   $1,032.20   $1,032.10