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 $68.40   11.826%   $76.489   $76.49   $76.50   $76.50  
  Purchase #2 $194.28   9.489%   $212.7152   $212.72   $212.70   $212.70  
  Purchase #3 $197.68   8.245%   $213.9787   $213.98   $214.00   $214.00  
  Purchase #4 $32.27   7.365%   $34.6467   $34.65   $34.65   $34.60  
  Purchase #5 $201.77   9.174%   $220.2804   $220.28   $220.30   $220.30  
  Purchase #6 $230.97   11.750%   $258.109   $258.11   $258.10   $258.10  
  Purchase #7 $205.61   7.423%   $220.8724   $220.87   $220.85   $220.90  
  7 purchase totals = $1,130.98       $1,237.0914   $1,237.10   $1,237.10   $1,237.10