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 $141.69   7.678%   $152.569   $152.57   $152.55   $152.60  
  Purchase #2 $114.48   8.365%   $124.0563   $124.06   $124.05   $124.10  
  Purchase #3 $244.55   7.591%   $263.1138   $263.11   $263.10   $263.10  
  Purchase #4 $107.34   11.628%   $119.8215   $119.82   $119.80   $119.80  
  Purchase #5 $107.64   5.587%   $113.6538   $113.65   $113.65   $113.70  
  Purchase #6 $248.72   7.491%   $267.3516   $267.35   $267.35   $267.40  
  Purchase #7 $119.66   9.658%   $131.2168   $131.22   $131.20   $131.20  
  7 purchase totals = $1,084.08       $1,171.7828   $1,171.78   $1,171.70   $1,171.90