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 $161.64   8.232%   $174.9462   $174.95   $174.95   $174.90  
  Purchase #2 $120.47   4.377%   $125.743   $125.74   $125.75   $125.70  
  Purchase #3 $39.26   6.775%   $41.9199   $41.92   $41.90   $41.90  
  Purchase #4 $46.47   5.369%   $48.965   $48.97   $48.95   $49.00  
  Purchase #5 $214.72   6.822%   $229.3682   $229.37   $229.35   $229.40  
  Purchase #6 $49.92   12.562%   $56.191   $56.19   $56.20   $56.20  
  Purchase #7 $196.57   5.384%   $207.1533   $207.15   $207.15   $207.20  
  7 purchase totals = $829.05       $884.2866   $884.29   $884.25   $884.30