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 $132.94   6.108%   $141.06   $141.06   $141.05   $141.10  
  Purchase #2 $217.33   8.383%   $235.5488   $235.55   $235.55   $235.50  
  Purchase #3 $191.42   12.213%   $214.7981   $214.80   $214.80   $214.80  
  Purchase #4 $164.96   10.553%   $182.3682   $182.37   $182.35   $182.40  
  Purchase #5 $211.63   6.346%   $225.06   $225.06   $225.05   $225.10  
  Purchase #6 $239.64   6.103%   $254.2652   $254.27   $254.25   $254.30  
  Purchase #7 $235.95   3.593%   $244.4277   $244.43   $244.45   $244.40  
  7 purchase totals = $1,393.87       $1,497.5280   $1,497.54   $1,497.50   $1,497.60