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 $84.42   9.133%   $92.1301   $92.13   $92.15   $92.10  
  Purchase #2 $196.92   4.222%   $205.234   $205.23   $205.25   $205.20  
  Purchase #3 $12.64   11.111%   $14.0444   $14.04   $14.05   $14.00  
  Purchase #4 $11.72   11.159%   $13.0278   $13.03   $13.05   $13.00  
  Purchase #5 $191.76   3.781%   $199.0104   $199.01   $199.00   $199.00  
  Purchase #6 $40.67   13.201%   $46.0388   $46.04   $46.05   $46.00  
  Purchase #7 $182.93   4.229%   $190.6661   $190.67   $190.65   $190.70  
  7 purchase totals = $721.06       $760.1516   $760.15   $760.20   $760.00