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 $65.57   3.691%   $67.9902   $67.99   $68.00   $68.00  
  Purchase #2 $152.64   8.492%   $165.6022   $165.60   $165.60   $165.60  
  Purchase #3 $159.51   11.702%   $178.1759   $178.18   $178.20   $178.20  
  Purchase #4 $121.58   4.530%   $127.0876   $127.09   $127.10   $127.10  
  Purchase #5 $226.49   4.809%   $237.3819   $237.38   $237.40   $237.40  
  Purchase #6 $94.42   4.759%   $98.9134   $98.91   $98.90   $98.90  
  Purchase #7 $125.65   13.149%   $142.1717   $142.17   $142.15   $142.20  
  7 purchase totals = $945.86       $1,017.3229   $1,017.32   $1,017.35   $1,017.40