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 $57.46   9.356%   $62.836   $62.84   $62.85   $62.80  
  Purchase #2 $202.76   3.611%   $210.0817   $210.08   $210.10   $210.10  
  Purchase #3 $173.42   7.560%   $186.5306   $186.53   $186.55   $186.50  
  Purchase #4 $173.45   8.728%   $188.5887   $188.59   $188.60   $188.60  
  Purchase #5 $187.26   4.566%   $195.8103   $195.81   $195.80   $195.80  
  Purchase #6 $135.98   6.547%   $144.8826   $144.88   $144.90   $144.90  
  Purchase #7 $173.92   13.333%   $197.1088   $197.11   $197.10   $197.10  
  7 purchase totals = $1,104.25       $1,185.8387   $1,185.84   $1,185.90   $1,185.80