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 $62.95   10.653%   $69.6561   $69.66   $69.65   $69.70  
  Purchase #2 $145.35   10.588%   $160.7397   $160.74   $160.75   $160.70  
  Purchase #3 $197.47   6.345%   $209.9995   $210.00   $210.00   $210.00  
  Purchase #4 $101.89   3.281%   $105.233   $105.23   $105.25   $105.20  
  Purchase #5 $115.72   3.591%   $119.8755   $119.88   $119.90   $119.90  
  Purchase #6 $45.36   9.806%   $49.808   $49.81   $49.80   $49.80  
  Purchase #7 $18.35   3.765%   $19.0409   $19.04   $19.05   $19.00  
  7 purchase totals = $687.09       $734.3527   $734.36   $734.40   $734.30