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 $182.77   6.326%   $194.332   $194.33   $194.35   $194.30  
  Purchase #2 $51.66   8.250%   $55.922   $55.92   $55.90   $55.90  
  Purchase #3 $178.82   10.502%   $197.5997   $197.60   $197.60   $197.60  
  Purchase #4 $17.25   6.758%   $18.4158   $18.42   $18.40   $18.40  
  Purchase #5 $123.99   4.144%   $129.1281   $129.13   $129.15   $129.10  
  Purchase #6 $144.75   5.119%   $152.1598   $152.16   $152.15   $152.20  
  Purchase #7 $83.64   7.191%   $89.6546   $89.65   $89.65   $89.70  
  7 purchase totals = $782.88       $837.2120   $837.21   $837.20   $837.20