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 $93.28   5.722%   $98.6175   $98.62   $98.60   $98.60  
  Purchase #2 $114.54   4.490%   $119.6828   $119.68   $119.70   $119.70  
  Purchase #3 $159.26   4.263%   $166.0493   $166.05   $166.05   $166.00  
  Purchase #4 $134.45   11.525%   $149.9454   $149.95   $149.95   $149.90  
  Purchase #5 $96.89   8.659%   $105.2797   $105.28   $105.30   $105.30  
  Purchase #6 $210.37   7.490%   $226.1267   $226.13   $226.15   $226.10  
  Purchase #7 $163.73   10.710%   $181.2655   $181.27   $181.25   $181.30  
  7 purchase totals = $972.52       $1,046.9669   $1,046.98   $1,047.00   $1,046.90