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 $59.32   5.804%   $62.7629   $62.76   $62.75   $62.80  
  Purchase #2 $166.77   13.441%   $189.1856   $189.19   $189.20   $189.20  
  Purchase #3 $195.76   10.616%   $216.5419   $216.54   $216.55   $216.50  
  Purchase #4 $247.62   6.526%   $263.7797   $263.78   $263.80   $263.80  
  Purchase #5 $10.35   10.336%   $11.4198   $11.42   $11.40   $11.40  
  Purchase #6 $35.77   9.318%   $39.103   $39.10   $39.10   $39.10  
  Purchase #7 $212.67   12.727%   $239.7365   $239.74   $239.75   $239.70  
  7 purchase totals = $928.26       $1,022.5294   $1,022.53   $1,022.55   $1,022.50