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 $64.99   5.601%   $68.6301   $68.63   $68.65   $68.60  
  Purchase #2 $162.26   10.735%   $179.6786   $179.68   $179.70   $179.70  
  Purchase #3 $29.32   8.825%   $31.9075   $31.91   $31.90   $31.90  
  Purchase #4 $204.82   5.597%   $216.2838   $216.28   $216.30   $216.30  
  Purchase #5 $185.89   11.569%   $207.3956   $207.40   $207.40   $207.40  
  Purchase #6 $247.36   5.280%   $260.4206   $260.42   $260.40   $260.40  
  Purchase #7 $83.37   3.399%   $86.2037   $86.20   $86.20   $86.20  
  7 purchase totals = $978.01       $1,050.5199   $1,050.52   $1,050.55   $1,050.50