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 $173.83   4.678%   $181.9618   $181.96   $181.95   $182.00  
  Purchase #2 $247.69   3.217%   $255.6582   $255.66   $255.65   $255.70  
  Purchase #3 $181.84   8.592%   $197.4637   $197.46   $197.45   $197.50  
  Purchase #4 $231.44   7.193%   $248.0875   $248.09   $248.10   $248.10  
  Purchase #5 $165.36   6.247%   $175.69   $175.69   $175.70   $175.70  
  Purchase #6 $123.91   9.593%   $135.7967   $135.80   $135.80   $135.80  
  Purchase #7 $35.45   5.389%   $37.3604   $37.36   $37.35   $37.40  
  7 purchase totals = $1,159.52       $1,232.0183   $1,232.02   $1,232.00   $1,232.20