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 $65.97   11.621%   $73.6364   $73.64   $73.65   $73.60  
  Purchase #2 $228.70   9.868%   $251.2681   $251.27   $251.25   $251.30  
  Purchase #3 $8.97   8.304%   $9.7149   $9.71   $9.70   $9.70  
  Purchase #4 $230.99   6.285%   $245.5077   $245.51   $245.50   $245.50  
  Purchase #5 $247.48   7.372%   $265.7242   $265.72   $265.70   $265.70  
  Purchase #6 $13.40   9.635%   $14.6911   $14.69   $14.70   $14.70  
  Purchase #7 $182.47   11.123%   $202.7661   $202.77   $202.75   $202.80  
  7 purchase totals = $977.98       $1,063.3085   $1,063.31   $1,063.25   $1,063.30