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 $249.66   5.541%   $263.4937   $263.49   $263.50   $263.50  
  Purchase #2 $203.86   7.271%   $218.6827   $218.68   $218.70   $218.70  
  Purchase #3 $219.97   9.660%   $241.2191   $241.22   $241.20   $241.20  
  Purchase #4 $76.52   12.746%   $86.2732   $86.27   $86.25   $86.30  
  Purchase #5 $56.81   5.634%   $60.0107   $60.01   $60.00   $60.00  
  Purchase #6 $98.43   6.281%   $104.6124   $104.61   $104.60   $104.60  
  Purchase #7 $38.88   3.624%   $40.289   $40.29   $40.30   $40.30  
  7 purchase totals = $944.13       $1,014.5808   $1,014.57   $1,014.55   $1,014.60