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 $184.49   5.307%   $194.2809   $194.28   $194.30   $194.30  
  Purchase #2 $233.71   10.736%   $258.8011   $258.80   $258.80   $258.80  
  Purchase #3 $46.25   5.163%   $48.6379   $48.64   $48.65   $48.60  
  Purchase #4 $134.72   3.821%   $139.8677   $139.87   $139.85   $139.90  
  Purchase #5 $186.97   9.749%   $205.1977   $205.20   $205.20   $205.20  
  Purchase #6 $173.64   9.613%   $190.332   $190.33   $190.35   $190.30  
  Purchase #7 $15.82   8.405%   $17.1497   $17.15   $17.15   $17.10  
  7 purchase totals = $975.60       $1,054.2670   $1,054.27   $1,054.30   $1,054.20