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 $68.36   12.465%   $76.8811   $76.88   $76.90   $76.90  
  Purchase #2 $61.51   4.628%   $64.3567   $64.36   $64.35   $64.40  
  Purchase #3 $44.90   3.324%   $46.3925   $46.39   $46.40   $46.40  
  Purchase #4 $221.38   11.346%   $246.4978   $246.50   $246.50   $246.50  
  Purchase #5 $183.92   6.729%   $196.296   $196.30   $196.30   $196.30  
  Purchase #6 $224.74   3.849%   $233.3902   $233.39   $233.40   $233.40  
  Purchase #7 $72.34   11.561%   $80.7032   $80.70   $80.70   $80.70  
  7 purchase totals = $877.15       $944.5175   $944.52   $944.55   $944.60