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 $217.97   6.259%   $231.6127   $231.61   $231.60   $231.60  
  Purchase #2 $245.64   5.653%   $259.526   $259.53   $259.55   $259.50  
  Purchase #3 $60.70   7.626%   $65.329   $65.33   $65.35   $65.30  
  Purchase #4 $32.88   5.303%   $34.6236   $34.62   $34.60   $34.60  
  Purchase #5 $160.64   9.532%   $175.9522   $175.95   $175.95   $176.00  
  Purchase #6 $188.35   12.749%   $212.3627   $212.36   $212.35   $212.40  
  Purchase #7 $127.59   6.236%   $135.5465   $135.55   $135.55   $135.50  
  7 purchase totals = $1,033.77       $1,114.9527   $1,114.95   $1,114.95   $1,114.90