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 $59.29   5.144%   $62.3399   $62.34   $62.35   $62.30  
  Purchase #2 $246.25   10.718%   $272.6431   $272.64   $272.65   $272.60  
  Purchase #3 $40.95   3.797%   $42.5049   $42.50   $42.50   $42.50  
  Purchase #4 $212.96   8.299%   $230.6336   $230.63   $230.65   $230.60  
  Purchase #5 $206.64   4.146%   $215.2073   $215.21   $215.20   $215.20  
  Purchase #6 $250.55   6.576%   $267.0262   $267.03   $267.05   $267.00  
  Purchase #7 $35.29   9.157%   $38.5215   $38.52   $38.50   $38.50  
  7 purchase totals = $1,051.93       $1,128.8765   $1,128.87   $1,128.90   $1,128.70