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 $214.95   13.156%   $243.2288   $243.23   $243.25   $243.20  
  Purchase #2 $220.47   10.162%   $242.8742   $242.87   $242.85   $242.90  
  Purchase #3 $22.90   4.832%   $24.0065   $24.01   $24.00   $24.00  
  Purchase #4 $14.41   7.730%   $15.5239   $15.52   $15.50   $15.50  
  Purchase #5 $206.88   8.628%   $224.7296   $224.73   $224.75   $224.70  
  Purchase #6 $43.52   3.544%   $45.0623   $45.06   $45.05   $45.10  
  Purchase #7 $230.95   6.637%   $246.2782   $246.28   $246.30   $246.30  
  7 purchase totals = $954.08       $1,041.7035   $1,041.70   $1,041.70   $1,041.70