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 $91.26   5.159%   $95.9681   $95.97   $95.95   $96.00  
  Purchase #2 $241.65   7.327%   $259.3557   $259.36   $259.35   $259.40  
  Purchase #3 $231.86   10.714%   $256.7015   $256.70   $256.70   $256.70  
  Purchase #4 $103.56   3.512%   $107.197   $107.20   $107.20   $107.20  
  Purchase #5 $172.86   3.615%   $179.1089   $179.11   $179.10   $179.10  
  Purchase #6 $238.51   3.119%   $245.9491   $245.95   $245.95   $245.90  
  Purchase #7 $226.92   12.563%   $255.428   $255.43   $255.45   $255.40  
  7 purchase totals = $1,306.62       $1,399.7083   $1,399.72   $1,399.70   $1,399.70