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 $57.52   8.298%   $62.293   $62.29   $62.30   $62.30  
  Purchase #2 $158.93   5.698%   $167.9858   $167.99   $168.00   $168.00  
  Purchase #3 $65.47   12.183%   $73.4462   $73.45   $73.45   $73.40  
  Purchase #4 $229.87   9.704%   $252.1766   $252.18   $252.20   $252.20  
  Purchase #5 $225.30   3.381%   $232.9174   $232.92   $232.90   $232.90  
  Purchase #6 $150.46   10.748%   $166.6314   $166.63   $166.65   $166.60  
  Purchase #7 $241.97   10.336%   $266.98   $266.98   $267.00   $267.00  
  7 purchase totals = $1,129.52       $1,222.4304   $1,222.44   $1,222.50   $1,222.40