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 $87.57   10.219%   $96.5188   $96.52   $96.50   $96.50  
  Purchase #2 $74.76   10.557%   $82.6524   $82.65   $82.65   $82.70  
  Purchase #3 $166.80   7.118%   $178.6728   $178.67   $178.65   $178.70  
  Purchase #4 $137.92   3.869%   $143.2561   $143.26   $143.25   $143.30  
  Purchase #5 $155.39   13.753%   $176.7608   $176.76   $176.75   $176.80  
  Purchase #6 $47.86   7.440%   $51.4208   $51.42   $51.40   $51.40  
  Purchase #7 $187.73   4.268%   $195.7423   $195.74   $195.75   $195.70  
  7 purchase totals = $858.03       $925.0240   $925.02   $924.95   $925.10