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 $67.98   11.752%   $75.969   $75.97   $75.95   $76.00  
  Purchase #2 $171.84   6.859%   $183.6265   $183.63   $183.65   $183.60  
  Purchase #3 $192.28   10.479%   $212.429   $212.43   $212.45   $212.40  
  Purchase #4 $230.53   13.411%   $261.4464   $261.45   $261.45   $261.40  
  Purchase #5 $216.87   3.107%   $223.6082   $223.61   $223.60   $223.60  
  Purchase #6 $157.36   9.824%   $172.819   $172.82   $172.80   $172.80  
  Purchase #7 $6.87   11.633%   $7.6692   $7.67   $7.65   $7.70  
  7 purchase totals = $1,043.73       $1,137.5673   $1,137.58   $1,137.55   $1,137.50