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 $191.53   5.254%   $201.593   $201.59   $201.60   $201.60  
  Purchase #2 $241.57   4.800%   $253.1654   $253.17   $253.15   $253.20  
  Purchase #3 $107.87   6.121%   $114.4727   $114.47   $114.45   $114.50  
  Purchase #4 $23.65   9.287%   $25.8464   $25.85   $25.85   $25.80  
  Purchase #5 $101.26   9.514%   $110.8939   $110.89   $110.90   $110.90  
  Purchase #6 $106.96   9.180%   $116.7789   $116.78   $116.80   $116.80  
  Purchase #7 $162.25   5.745%   $171.5713   $171.57   $171.55   $171.60  
  7 purchase totals = $935.09       $994.3216   $994.32   $994.30   $994.40