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 $212.41   13.780%   $241.6801   $241.68   $241.70   $241.70  
  Purchase #2 $45.93   5.155%   $48.2977   $48.30   $48.30   $48.30  
  Purchase #3 $203.97   8.576%   $221.4625   $221.46   $221.45   $221.50  
  Purchase #4 $55.72   12.528%   $62.7006   $62.70   $62.70   $62.70  
  Purchase #5 $197.51   4.603%   $206.6014   $206.60   $206.60   $206.60  
  Purchase #6 $159.26   11.305%   $177.2643   $177.26   $177.25   $177.30  
  Purchase #7 $39.72   6.485%   $42.2958   $42.30   $42.30   $42.30  
  7 purchase totals = $914.52       $1,000.3024   $1,000.30   $1,000.30   $1,000.40