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 $58.25   5.656%   $61.5446   $61.54   $61.55   $61.50  
  Purchase #2 $187.98   6.214%   $199.6611   $199.66   $199.65   $199.70  
  Purchase #3 $211.29   10.855%   $234.2255   $234.23   $234.25   $234.20  
  Purchase #4 $11.28   3.726%   $11.7003   $11.70   $11.70   $11.70  
  Purchase #5 $172.30   12.159%   $193.25   $193.25   $193.25   $193.30  
  Purchase #6 $88.71   13.852%   $100.9981   $101.00   $101.00   $101.00  
  Purchase #7 $189.40   12.713%   $213.4784   $213.48   $213.50   $213.50  
  7 purchase totals = $919.21       $1,014.8580   $1,014.86   $1,014.90   $1,014.90