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 $201.67   7.255%   $216.3012   $216.30   $216.30   $216.30  
  Purchase #2 $213.93   9.198%   $233.6073   $233.61   $233.60   $233.60  
  Purchase #3 $207.78   7.794%   $223.9744   $223.97   $223.95   $224.00  
  Purchase #4 $45.74   8.318%   $49.5447   $49.54   $49.55   $49.50  
  Purchase #5 $162.87   7.680%   $175.3784   $175.38   $175.40   $175.40  
  Purchase #6 $167.92   5.468%   $177.1019   $177.10   $177.10   $177.10  
  Purchase #7 $119.46   6.846%   $127.6382   $127.64   $127.65   $127.60  
  7 purchase totals = $1,119.37       $1,203.5461   $1,203.54   $1,203.55   $1,203.50