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 $96.33   9.217%   $105.2087   $105.21   $105.20   $105.20  
  Purchase #2 $191.99   5.597%   $202.7357   $202.74   $202.75   $202.70  
  Purchase #3 $236.32   8.671%   $256.8113   $256.81   $256.80   $256.80  
  Purchase #4 $56.95   6.850%   $60.8511   $60.85   $60.85   $60.90  
  Purchase #5 $218.63   11.840%   $244.5158   $244.52   $244.50   $244.50  
  Purchase #6 $239.78   5.827%   $253.752   $253.75   $253.75   $253.80  
  Purchase #7 $85.82   10.851%   $95.1323   $95.13   $95.15   $95.10  
  7 purchase totals = $1,125.82       $1,219.0069   $1,219.01   $1,219.00   $1,219.00