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 $67.51   9.310%   $73.7952   $73.80   $73.80   $73.80  
  Purchase #2 $43.51   9.601%   $47.6874   $47.69   $47.70   $47.70  
  Purchase #3 $103.68   7.591%   $111.5503   $111.55   $111.55   $111.60  
  Purchase #4 $198.99   6.628%   $212.1791   $212.18   $212.20   $212.20  
  Purchase #5 $179.98   5.238%   $189.4074   $189.41   $189.40   $189.40  
  Purchase #6 $200.52   6.530%   $213.614   $213.61   $213.60   $213.60  
  Purchase #7 $110.75   7.517%   $119.0751   $119.08   $119.10   $119.10  
  7 purchase totals = $904.94       $967.3085   $967.32   $967.35   $967.40