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 $232.87   3.809%   $241.74   $241.74   $241.75   $241.70  
  Purchase #2 $118.72   13.436%   $134.6712   $134.67   $134.65   $134.70  
  Purchase #3 $52.76   13.307%   $59.7808   $59.78   $59.80   $59.80  
  Purchase #4 $233.90   8.534%   $253.861   $253.86   $253.85   $253.90  
  Purchase #5 $142.69   5.276%   $150.2183   $150.22   $150.20   $150.20  
  Purchase #6 $112.69   8.685%   $122.4771   $122.48   $122.50   $122.50  
  Purchase #7 $176.64   12.807%   $199.2623   $199.26   $199.25   $199.30  
  7 purchase totals = $1,070.27       $1,162.0107   $1,162.01   $1,162.00   $1,162.10