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 $63.44   9.648%   $69.5607   $69.56   $69.55   $69.60  
  Purchase #2 $168.55   10.494%   $186.2376   $186.24   $186.25   $186.20  
  Purchase #3 $230.94   9.267%   $252.3412   $252.34   $252.35   $252.30  
  Purchase #4 $171.67   13.235%   $194.3905   $194.39   $194.40   $194.40  
  Purchase #5 $218.52   9.130%   $238.4709   $238.47   $238.45   $238.50  
  Purchase #6 $231.25   6.661%   $246.6536   $246.65   $246.65   $246.70  
  Purchase #7 $27.68   11.614%   $30.8948   $30.89   $30.90   $30.90  
  7 purchase totals = $1,112.05       $1,218.5493   $1,218.54   $1,218.55   $1,218.60