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 $90.95   4.541%   $95.08   $95.08   $95.10   $95.10  
  Purchase #2 $178.93   11.575%   $199.6411   $199.64   $199.65   $199.60  
  Purchase #3 $61.44   4.440%   $64.1679   $64.17   $64.15   $64.20  
  Purchase #4 $171.65   10.743%   $190.0904   $190.09   $190.10   $190.10  
  Purchase #5 $21.66   13.744%   $24.637   $24.64   $24.65   $24.60  
  Purchase #6 $70.26   9.767%   $77.1223   $77.12   $77.10   $77.10  
  Purchase #7 $119.92   5.625%   $126.6655   $126.67   $126.65   $126.70  
  7 purchase totals = $714.81       $777.4042   $777.41   $777.40   $777.40