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 $168.90   4.393%   $176.3198   $176.32   $176.30   $176.30  
  Purchase #2 $246.68   9.289%   $269.5941   $269.59   $269.60   $269.60  
  Purchase #3 $216.60   7.320%   $232.4551   $232.46   $232.45   $232.50  
  Purchase #4 $199.83   6.374%   $212.5672   $212.57   $212.55   $212.60  
  Purchase #5 $46.99   5.129%   $49.4001   $49.40   $49.40   $49.40  
  Purchase #6 $165.99   9.619%   $181.9566   $181.96   $181.95   $182.00  
  Purchase #7 $158.55   13.794%   $180.4204   $180.42   $180.40   $180.40  
  7 purchase totals = $1,203.54       $1,302.7133   $1,302.72   $1,302.65   $1,302.80