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 $183.97   9.766%   $201.9365   $201.94   $201.95   $201.90  
  Purchase #2 $57.84   3.347%   $59.7759   $59.78   $59.80   $59.80  
  Purchase #3 $177.70   8.150%   $192.1826   $192.18   $192.20   $192.20  
  Purchase #4 $83.36   5.611%   $88.0373   $88.04   $88.05   $88.00  
  Purchase #5 $41.68   3.405%   $43.0992   $43.10   $43.10   $43.10  
  Purchase #6 $239.48   12.336%   $269.0223   $269.02   $269.00   $269.00  
  Purchase #7 $188.68   13.871%   $214.8518   $214.85   $214.85   $214.90  
  7 purchase totals = $972.71       $1,068.9056   $1,068.91   $1,068.95   $1,068.90