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 $89.61   7.302%   $96.1533   $96.15   $96.15   $96.20  
  Purchase #2 $88.81   5.445%   $93.6457   $93.65   $93.65   $93.60  
  Purchase #3 $8.76   6.166%   $9.3001   $9.30   $9.30   $9.30  
  Purchase #4 $212.73   10.250%   $234.5348   $234.53   $234.55   $234.50  
  Purchase #5 $62.57   7.145%   $67.0406   $67.04   $67.05   $67.00  
  Purchase #6 $120.81   4.293%   $125.9964   $126.00   $126.00   $126.00  
  Purchase #7 $74.89   6.716%   $79.9196   $79.92   $79.90   $79.90  
  7 purchase totals = $658.18       $706.5905   $706.59   $706.60   $706.50