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 $222.87   5.785%   $235.763   $235.76   $235.75   $235.80  
  Purchase #2 $226.48   10.698%   $250.7088   $250.71   $250.70   $250.70  
  Purchase #3 $127.99   5.382%   $134.8784   $134.88   $134.90   $134.90  
  Purchase #4 $242.59   9.268%   $265.0732   $265.07   $265.05   $265.10  
  Purchase #5 $87.52   4.533%   $91.4873   $91.49   $91.50   $91.50  
  Purchase #6 $228.35   6.811%   $243.9029   $243.90   $243.90   $243.90  
  Purchase #7 $238.75   6.715%   $254.7821   $254.78   $254.80   $254.80  
  7 purchase totals = $1,374.55       $1,476.5957   $1,476.59   $1,476.60   $1,476.70