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 $195.54   8.281%   $211.7327   $211.73   $211.75   $211.70  
  Purchase #2 $238.85   4.458%   $249.4979   $249.50   $249.50   $249.50  
  Purchase #3 $20.33   5.446%   $21.4372   $21.44   $21.45   $21.40  
  Purchase #4 $49.36   6.771%   $52.7022   $52.70   $52.70   $52.70  
  Purchase #5 $171.85   13.763%   $195.5017   $195.50   $195.50   $195.50  
  Purchase #6 $218.85   5.276%   $230.3965   $230.40   $230.40   $230.40  
  Purchase #7 $60.82   12.312%   $68.3082   $68.31   $68.30   $68.30  
  7 purchase totals = $955.60       $1,029.5764   $1,029.58   $1,029.60   $1,029.50