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 $183.51   6.284%   $195.0418   $195.04   $195.05   $195.00  
  Purchase #2 $138.36   13.508%   $157.0497   $157.05   $157.05   $157.00  
  Purchase #3 $188.99   3.188%   $195.015   $195.02   $195.00   $195.00  
  Purchase #4 $185.81   13.850%   $211.5447   $211.54   $211.55   $211.50  
  Purchase #5 $95.95   4.181%   $99.9617   $99.96   $99.95   $100.00  
  Purchase #6 $23.43   11.814%   $26.198   $26.20   $26.20   $26.20  
  Purchase #7 $147.75   7.602%   $158.982   $158.98   $159.00   $159.00  
  7 purchase totals = $963.80       $1,043.7929   $1,043.79   $1,043.80   $1,043.70