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 $207.64   7.871%   $223.9833   $223.98   $224.00   $224.00  
  Purchase #2 $219.97   11.578%   $245.4381   $245.44   $245.45   $245.40  
  Purchase #3 $59.47   6.544%   $63.3617   $63.36   $63.35   $63.40  
  Purchase #4 $38.43   6.296%   $40.8496   $40.85   $40.85   $40.80  
  Purchase #5 $232.72   4.400%   $242.9597   $242.96   $242.95   $243.00  
  Purchase #6 $44.97   8.861%   $48.9548   $48.95   $48.95   $49.00  
  Purchase #7 $207.35   11.735%   $231.6825   $231.68   $231.70   $231.70  
  7 purchase totals = $1,010.55       $1,097.2297   $1,097.22   $1,097.25   $1,097.30