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 $125.78   6.767%   $134.2915   $134.29   $134.30   $134.30  
  Purchase #2 $232.70   8.145%   $251.6534   $251.65   $251.65   $251.70  
  Purchase #3 $54.82   6.531%   $58.4003   $58.40   $58.40   $58.40  
  Purchase #4 $106.33   4.431%   $111.0415   $111.04   $111.05   $111.00  
  Purchase #5 $115.86   11.750%   $129.4736   $129.47   $129.45   $129.50  
  Purchase #6 $40.95   5.828%   $43.3366   $43.34   $43.35   $43.30  
  Purchase #7 $44.64   7.419%   $47.9518   $47.95   $47.95   $48.00  
  7 purchase totals = $721.08       $776.1487   $776.14   $776.15   $776.20