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 $67.63   13.313%   $76.6336   $76.63   $76.65   $76.60  
  Purchase #2 $113.53   9.543%   $124.3642   $124.36   $124.35   $124.40  
  Purchase #3 $213.81   11.279%   $237.9256   $237.93   $237.95   $237.90  
  Purchase #4 $242.70   12.490%   $273.0132   $273.01   $273.00   $273.00  
  Purchase #5 $74.36   3.178%   $76.7232   $76.72   $76.70   $76.70  
  Purchase #6 $198.66   12.472%   $223.4369   $223.44   $223.45   $223.40  
  Purchase #7 $184.78   9.333%   $202.0255   $202.03   $202.05   $202.00  
  7 purchase totals = $1,095.47       $1,214.1222   $1,214.12   $1,214.15   $1,214.00