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 $32.76   5.595%   $34.5929   $34.59   $34.60   $34.60  
  Purchase #2 $240.79   6.311%   $255.9863   $255.99   $256.00   $256.00  
  Purchase #3 $55.97   3.314%   $57.8248   $57.82   $57.80   $57.80  
  Purchase #4 $85.74   12.617%   $96.5578   $96.56   $96.55   $96.60  
  Purchase #5 $235.90   11.406%   $262.8068   $262.81   $262.80   $262.80  
  Purchase #6 $210.89   9.161%   $230.2096   $230.21   $230.20   $230.20  
  Purchase #7 $145.84   8.780%   $158.6448   $158.64   $158.65   $158.60  
  7 purchase totals = $1,007.89       $1,096.6230   $1,096.62   $1,096.60   $1,096.60