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 $163.65   7.608%   $176.1005   $176.10   $176.10   $176.10  
  Purchase #2 $177.93   7.269%   $190.8637   $190.86   $190.85   $190.90  
  Purchase #3 $8.58   3.816%   $8.9074   $8.91   $8.90   $8.90  
  Purchase #4 $236.66   4.620%   $247.5937   $247.59   $247.60   $247.60  
  Purchase #5 $22.34   10.840%   $24.7617   $24.76   $24.75   $24.80  
  Purchase #6 $207.54   7.322%   $222.7361   $222.74   $222.75   $222.70  
  Purchase #7 $226.31   3.292%   $233.7601   $233.76   $233.75   $233.80  
  7 purchase totals = $1,043.01       $1,104.7232   $1,104.72   $1,104.70   $1,104.80