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 $41.65   3.294%   $43.022   $43.02   $43.00   $43.00  
  Purchase #2 $164.36   7.461%   $176.6229   $176.62   $176.60   $176.60  
  Purchase #3 $140.73   9.552%   $154.1725   $154.17   $154.15   $154.20  
  Purchase #4 $109.72   5.590%   $115.8533   $115.85   $115.85   $115.90  
  Purchase #5 $150.86   7.787%   $162.6075   $162.61   $162.60   $162.60  
  Purchase #6 $200.93   5.658%   $212.2986   $212.30   $212.30   $212.30  
  Purchase #7 $57.28   6.442%   $60.97   $60.97   $60.95   $61.00  
  7 purchase totals = $865.53       $925.5468   $925.54   $925.45   $925.60