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 $85.32   11.470%   $95.1062   $95.11   $95.10   $95.10  
  Purchase #2 $181.96   11.778%   $203.3912   $203.39   $203.40   $203.40  
  Purchase #3 $72.81   8.171%   $78.7593   $78.76   $78.75   $78.80  
  Purchase #4 $22.43   11.418%   $24.9911   $24.99   $25.00   $25.00  
  Purchase #5 $222.79   13.204%   $252.2072   $252.21   $252.20   $252.20  
  Purchase #6 $213.43   9.110%   $232.8735   $232.87   $232.85   $232.90  
  Purchase #7 $14.67   4.618%   $15.3475   $15.35   $15.35   $15.30  
  7 purchase totals = $813.41       $902.6760   $902.68   $902.65   $902.70