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 $105.61   11.137%   $117.3718   $117.37   $117.35   $117.40  
  Purchase #2 $215.99   6.193%   $229.3663   $229.37   $229.35   $229.40  
  Purchase #3 $147.67   4.117%   $153.7496   $153.75   $153.75   $153.70  
  Purchase #4 $210.25   4.800%   $220.342   $220.34   $220.35   $220.30  
  Purchase #5 $246.41   7.746%   $265.4969   $265.50   $265.50   $265.50  
  Purchase #6 $159.86   13.387%   $181.2605   $181.26   $181.25   $181.30  
  Purchase #7 $177.47   12.698%   $200.0051   $200.01   $200.00   $200.00  
  7 purchase totals = $1,263.26       $1,367.5922   $1,367.60   $1,367.55   $1,367.60