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 $233.95   12.252%   $262.6136   $262.61   $262.60   $262.60  
  Purchase #2 $167.35   4.270%   $174.4958   $174.50   $174.50   $174.50  
  Purchase #3 $60.97   12.359%   $68.5053   $68.51   $68.50   $68.50  
  Purchase #4 $177.69   3.729%   $184.3161   $184.32   $184.30   $184.30  
  Purchase #5 $119.49   4.560%   $124.9387   $124.94   $124.95   $124.90  
  Purchase #6 $46.95   13.511%   $53.2934   $53.29   $53.30   $53.30  
  Purchase #7 $145.45   8.833%   $158.2976   $158.30   $158.30   $158.30  
  7 purchase totals = $951.85       $1,026.4605   $1,026.47   $1,026.45   $1,026.40