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 $195.77   7.798%   $211.0361   $211.04   $211.05   $211.00  
  Purchase #2 $168.93   13.377%   $191.5278   $191.53   $191.55   $191.50  
  Purchase #3 $142.46   7.375%   $152.9664   $152.97   $152.95   $153.00  
  Purchase #4 $143.80   11.196%   $159.8998   $159.90   $159.90   $159.90  
  Purchase #5 $89.27   6.418%   $94.9993   $95.00   $95.00   $95.00  
  Purchase #6 $14.43   8.704%   $15.686   $15.69   $15.70   $15.70  
  Purchase #7 $147.91   8.355%   $160.2679   $160.27   $160.25   $160.30  
  7 purchase totals = $902.57       $986.3833   $986.40   $986.40   $986.40