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 $214.60   10.368%   $236.8497   $236.85   $236.85   $236.80  
  Purchase #2 $12.43   10.170%   $13.6941   $13.69   $13.70   $13.70  
  Purchase #3 $67.30   4.350%   $70.2276   $70.23   $70.25   $70.20  
  Purchase #4 $7.40   11.385%   $8.2425   $8.24   $8.25   $8.20  
  Purchase #5 $185.45   6.358%   $197.2409   $197.24   $197.25   $197.20  
  Purchase #6 $200.51   3.279%   $207.0847   $207.08   $207.10   $207.10  
  Purchase #7 $56.66   10.164%   $62.4189   $62.42   $62.40   $62.40  
  7 purchase totals = $744.35       $795.7584   $795.75   $795.80   $795.60