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 $131.61   7.323%   $141.2478   $141.25   $141.25   $141.20  
  Purchase #2 $238.91   5.751%   $252.6497   $252.65   $252.65   $252.60  
  Purchase #3 $237.36   9.827%   $260.6854   $260.69   $260.70   $260.70  
  Purchase #4 $163.39   11.143%   $181.5965   $181.60   $181.60   $181.60  
  Purchase #5 $105.63   4.257%   $110.1267   $110.13   $110.15   $110.10  
  Purchase #6 $123.49   9.610%   $135.3574   $135.36   $135.35   $135.40  
  Purchase #7 $60.52   8.652%   $65.7562   $65.76   $65.75   $65.80  
  7 purchase totals = $1,060.91       $1,147.4197   $1,147.44   $1,147.45   $1,147.40