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 $228.39   5.524%   $241.0063   $241.01   $241.00   $241.00  
  Purchase #2 $218.76   8.407%   $237.1512   $237.15   $237.15   $237.20  
  Purchase #3 $246.80   7.625%   $265.6185   $265.62   $265.60   $265.60  
  Purchase #4 $218.36   10.556%   $241.4101   $241.41   $241.40   $241.40  
  Purchase #5 $235.52   10.473%   $260.186   $260.19   $260.20   $260.20  
  Purchase #6 $93.47   6.305%   $99.3633   $99.36   $99.35   $99.40  
  Purchase #7 $221.91   3.250%   $229.1221   $229.12   $229.10   $229.10  
  7 purchase totals = $1,463.21       $1,573.8575   $1,573.86   $1,573.80   $1,573.90