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 $87.65   11.751%   $97.9498   $97.95   $97.95   $97.90  
  Purchase #2 $167.83   10.412%   $185.3045   $185.30   $185.30   $185.30  
  Purchase #3 $246.67   10.551%   $272.6962   $272.70   $272.70   $272.70  
  Purchase #4 $183.61   7.203%   $196.8354   $196.84   $196.85   $196.80  
  Purchase #5 $175.88   3.357%   $181.7843   $181.78   $181.80   $181.80  
  Purchase #6 $18.61   3.412%   $19.245   $19.25   $19.25   $19.20  
  Purchase #7 $72.74   9.340%   $79.5339   $79.53   $79.55   $79.50  
  7 purchase totals = $952.99       $1,033.3491   $1,033.35   $1,033.40   $1,033.20