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 $208.64   10.726%   $231.0187   $231.02   $231.00   $231.00  
  Purchase #2 $86.99   10.357%   $95.9996   $96.00   $96.00   $96.00  
  Purchase #3 $69.84   10.466%   $77.1495   $77.15   $77.15   $77.10  
  Purchase #4 $197.96   6.427%   $210.6829   $210.68   $210.70   $210.70  
  Purchase #5 $136.52   11.246%   $151.873   $151.87   $151.85   $151.90  
  Purchase #6 $234.65   12.845%   $264.7908   $264.79   $264.80   $264.80  
  Purchase #7 $88.69   10.362%   $97.8801   $97.88   $97.90   $97.90  
  7 purchase totals = $1,023.29       $1,129.3946   $1,129.39   $1,129.40   $1,129.40