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 $195.81   5.195%   $205.9823   $205.98   $206.00   $206.00  
  Purchase #2 $33.38   7.194%   $35.7814   $35.78   $35.80   $35.80  
  Purchase #3 $243.82   3.457%   $252.2489   $252.25   $252.25   $252.20  
  Purchase #4 $207.41   9.632%   $227.3877   $227.39   $227.40   $227.40  
  Purchase #5 $230.92   6.373%   $245.6365   $245.64   $245.65   $245.60  
  Purchase #6 $110.42   11.825%   $123.4772   $123.48   $123.50   $123.50  
  Purchase #7 $23.25   5.456%   $24.5185   $24.52   $24.50   $24.50  
  7 purchase totals = $1,045.01       $1,115.0325   $1,115.04   $1,115.10   $1,115.00