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 $174.80   11.612%   $195.0978   $195.10   $195.10   $195.10  
  Purchase #2 $238.28   9.817%   $261.6719   $261.67   $261.65   $261.70  
  Purchase #3 $33.50   4.749%   $35.0909   $35.09   $35.10   $35.10  
  Purchase #4 $144.85   3.612%   $150.082   $150.08   $150.10   $150.10  
  Purchase #5 $76.76   3.406%   $79.3744   $79.37   $79.35   $79.40  
  Purchase #6 $160.59   4.569%   $167.9274   $167.93   $167.95   $167.90  
  Purchase #7 $57.90   7.630%   $62.3178   $62.32   $62.30   $62.30  
  7 purchase totals = $886.68       $951.5622   $951.56   $951.55   $951.60