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 $195.46   5.710%   $206.6208   $206.62   $206.60   $206.60  
  Purchase #2 $44.49   9.353%   $48.6511   $48.65   $48.65   $48.70  
  Purchase #3 $84.43   9.576%   $92.515   $92.52   $92.50   $92.50  
  Purchase #4 $89.77   7.247%   $96.2756   $96.28   $96.30   $96.30  
  Purchase #5 $57.63   6.748%   $61.5189   $61.52   $61.50   $61.50  
  Purchase #6 $122.31   13.466%   $138.7803   $138.78   $138.80   $138.80  
  Purchase #7 $86.90   5.342%   $91.5422   $91.54   $91.55   $91.50  
  7 purchase totals = $680.99       $735.9039   $735.91   $735.90   $735.90