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 $180.28   11.656%   $201.2934   $201.29   $201.30   $201.30  
  Purchase #2 $48.53   10.620%   $53.6839   $53.68   $53.70   $53.70  
  Purchase #3 $156.74   5.651%   $165.5974   $165.60   $165.60   $165.60  
  Purchase #4 $22.29   3.298%   $23.0251   $23.03   $23.05   $23.00  
  Purchase #5 $174.77   13.143%   $197.74   $197.74   $197.75   $197.70  
  Purchase #6 $228.40   4.108%   $237.7827   $237.78   $237.80   $237.80  
  Purchase #7 $239.46   9.870%   $263.0947   $263.09   $263.10   $263.10  
  7 purchase totals = $1,050.47       $1,142.2172   $1,142.21   $1,142.30   $1,142.20