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 $76.60   5.234%   $80.6092   $80.61   $80.60   $80.60  
  Purchase #2 $224.52   9.400%   $245.6249   $245.62   $245.60   $245.60  
  Purchase #3 $81.64   8.573%   $88.639   $88.64   $88.65   $88.60  
  Purchase #4 $123.95   12.278%   $139.1686   $139.17   $139.15   $139.20  
  Purchase #5 $212.81   4.774%   $222.9695   $222.97   $222.95   $223.00  
  Purchase #6 $71.77   8.491%   $77.864   $77.86   $77.85   $77.90  
  Purchase #7 $221.66   11.530%   $247.2174   $247.22   $247.20   $247.20  
  7 purchase totals = $1,012.95       $1,102.0926   $1,102.09   $1,102.00   $1,102.10