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 $197.82   5.245%   $208.1957   $208.20   $208.20   $208.20  
  Purchase #2 $96.78   8.180%   $104.6966   $104.70   $104.70   $104.70  
  Purchase #3 $147.57   6.345%   $156.9333   $156.93   $156.95   $156.90  
  Purchase #4 $123.75   3.168%   $127.6704   $127.67   $127.65   $127.70  
  Purchase #5 $232.96   12.580%   $262.2664   $262.27   $262.25   $262.30  
  Purchase #6 $59.39   5.569%   $62.6974   $62.70   $62.70   $62.70  
  Purchase #7 $67.26   9.160%   $73.421   $73.42   $73.40   $73.40  
  7 purchase totals = $925.53       $995.8808   $995.89   $995.85   $995.90