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 $210.37   10.553%   $232.5703   $232.57   $232.55   $232.60  
  Purchase #2 $185.78   11.666%   $207.4531   $207.45   $207.45   $207.50  
  Purchase #3 $127.69   10.114%   $140.6046   $140.60   $140.60   $140.60  
  Purchase #4 $191.30   4.333%   $199.589   $199.59   $199.60   $199.60  
  Purchase #5 $76.84   8.866%   $83.6526   $83.65   $83.65   $83.70  
  Purchase #6 $210.60   8.403%   $228.2967   $228.30   $228.30   $228.30  
  Purchase #7 $212.96   9.812%   $233.8556   $233.86   $233.85   $233.90  
  7 purchase totals = $1,215.54       $1,326.0219   $1,326.02   $1,326.00   $1,326.20