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 $54.86   10.522%   $60.6324   $60.63   $60.65   $60.60  
  Purchase #2 $207.77   13.213%   $235.2227   $235.22   $235.20   $235.20  
  Purchase #3 $101.67   7.642%   $109.4396   $109.44   $109.45   $109.40  
  Purchase #4 $182.89   10.420%   $201.9471   $201.95   $201.95   $201.90  
  Purchase #5 $210.28   3.667%   $217.991   $217.99   $218.00   $218.00  
  Purchase #6 $137.68   6.601%   $146.7683   $146.77   $146.75   $146.80  
  Purchase #7 $33.61   8.568%   $36.4897   $36.49   $36.50   $36.50  
  7 purchase totals = $928.76       $1,008.4908   $1,008.49   $1,008.50   $1,008.40