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 $54.27   12.307%   $60.949   $60.95   $60.95   $60.90  
  Purchase #2 $24.78   3.658%   $25.6865   $25.69   $25.70   $25.70  
  Purchase #3 $162.89   11.545%   $181.6957   $181.70   $181.70   $181.70  
  Purchase #4 $78.58   9.659%   $86.17   $86.17   $86.15   $86.20  
  Purchase #5 $20.27   7.130%   $21.7153   $21.72   $21.70   $21.70  
  Purchase #6 $11.55   5.686%   $12.2067   $12.21   $12.20   $12.20  
  Purchase #7 $23.90   5.849%   $25.2979   $25.30   $25.30   $25.30  
  7 purchase totals = $376.24       $413.7211   $413.74   $413.70   $413.70