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 $62.50   7.594%   $67.2463   $67.25   $67.25   $67.20  
  Purchase #2 $62.48   11.498%   $69.664   $69.66   $69.65   $69.70  
  Purchase #3 $202.61   5.397%   $213.5449   $213.54   $213.55   $213.50  
  Purchase #4 $103.26   6.549%   $110.0225   $110.02   $110.00   $110.00  
  Purchase #5 $189.69   6.236%   $201.5191   $201.52   $201.50   $201.50  
  Purchase #6 $200.51   3.711%   $207.9509   $207.95   $207.95   $208.00  
  Purchase #7 $72.26   11.324%   $80.4427   $80.44   $80.45   $80.40  
  7 purchase totals = $893.31       $950.3904   $950.38   $950.35   $950.30