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 $212.32   7.646%   $228.554   $228.55   $228.55   $228.60  
  Purchase #2 $67.26   10.750%   $74.4905   $74.49   $74.50   $74.50  
  Purchase #3 $110.81   6.810%   $118.3562   $118.36   $118.35   $118.40  
  Purchase #4 $97.75   9.462%   $106.9991   $107.00   $107.00   $107.00  
  Purchase #5 $155.25   9.306%   $169.6976   $169.70   $169.70   $169.70  
  Purchase #6 $241.44   3.748%   $250.4892   $250.49   $250.50   $250.50  
  Purchase #7 $67.38   11.804%   $75.3335   $75.33   $75.35   $75.30  
  7 purchase totals = $952.21       $1,023.9201   $1,023.92   $1,023.95   $1,024.00