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 $69.95   11.295%   $77.8509   $77.85   $77.85   $77.90  
  Purchase #2 $195.89   7.176%   $209.9471   $209.95   $209.95   $209.90  
  Purchase #3 $12.62   10.818%   $13.9852   $13.99   $14.00   $14.00  
  Purchase #4 $167.66   8.530%   $181.9614   $181.96   $181.95   $182.00  
  Purchase #5 $75.77   3.735%   $78.6   $78.60   $78.60   $78.60  
  Purchase #6 $74.35   12.214%   $83.4311   $83.43   $83.45   $83.40  
  Purchase #7 $68.27   13.782%   $77.679   $77.68   $77.70   $77.70  
  7 purchase totals = $664.51       $723.4547   $723.46   $723.50   $723.50