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 $96.99   8.516%   $105.2497   $105.25   $105.25   $105.20  
  Purchase #2 $127.87   7.299%   $137.2032   $137.20   $137.20   $137.20  
  Purchase #3 $65.76   11.533%   $73.3441   $73.34   $73.35   $73.30  
  Purchase #4 $145.29   5.510%   $153.2955   $153.30   $153.30   $153.30  
  Purchase #5 $56.34   4.737%   $59.0088   $59.01   $59.00   $59.00  
  Purchase #6 $132.95   4.502%   $138.9354   $138.94   $138.95   $138.90  
  Purchase #7 $80.30   6.130%   $85.2224   $85.22   $85.20   $85.20  
  7 purchase totals = $705.50       $752.2591   $752.26   $752.25   $752.10