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 $58.37   5.769%   $61.7374   $61.74   $61.75   $61.70  
  Purchase #2 $156.75   3.343%   $161.9902   $161.99   $162.00   $162.00  
  Purchase #3 $11.51   4.273%   $12.0018   $12.00   $12.00   $12.00  
  Purchase #4 $193.92   4.456%   $202.5611   $202.56   $202.55   $202.60  
  Purchase #5 $167.49   3.828%   $173.9015   $173.90   $173.90   $173.90  
  Purchase #6 $212.86   13.520%   $241.6387   $241.64   $241.65   $241.60  
  Purchase #7 $128.35   13.670%   $145.8954   $145.90   $145.90   $145.90  
  7 purchase totals = $929.25       $999.7261   $999.73   $999.75   $999.70