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 $49.48   8.704%   $53.7867   $53.79   $53.80   $53.80  
  Purchase #2 $58.67   9.218%   $64.0782   $64.08   $64.10   $64.10  
  Purchase #3 $86.54   9.191%   $94.4939   $94.49   $94.50   $94.50  
  Purchase #4 $220.99   6.117%   $234.508   $234.51   $234.50   $234.50  
  Purchase #5 $152.31   6.321%   $161.9375   $161.94   $161.95   $161.90  
  Purchase #6 $226.66   8.771%   $246.5403   $246.54   $246.55   $246.50  
  Purchase #7 $222.76   12.383%   $250.3444   $250.34   $250.35   $250.30  
  7 purchase totals = $1,017.41       $1,105.6890   $1,105.69   $1,105.75   $1,105.60