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 $118.86   5.480%   $125.3735   $125.37   $125.35   $125.40  
  Purchase #2 $250.49   6.384%   $266.4813   $266.48   $266.50   $266.50  
  Purchase #3 $89.32   7.463%   $95.986   $95.99   $96.00   $96.00  
  Purchase #4 $158.98   6.629%   $169.5188   $169.52   $169.50   $169.50  
  Purchase #5 $56.57   6.687%   $60.3528   $60.35   $60.35   $60.40  
  Purchase #6 $64.27   5.325%   $67.6924   $67.69   $67.70   $67.70  
  Purchase #7 $119.55   12.288%   $134.2403   $134.24   $134.25   $134.20  
  7 purchase totals = $858.04       $919.6451   $919.64   $919.65   $919.70