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 $61.26   3.512%   $63.4115   $63.41   $63.40   $63.40  
  Purchase #2 $154.33   7.344%   $165.664   $165.66   $165.65   $165.70  
  Purchase #3 $33.51   6.749%   $35.7716   $35.77   $35.75   $35.80  
  Purchase #4 $113.86   12.662%   $128.277   $128.28   $128.30   $128.30  
  Purchase #5 $219.75   12.216%   $246.5947   $246.59   $246.60   $246.60  
  Purchase #6 $194.68   6.782%   $207.8832   $207.88   $207.90   $207.90  
  Purchase #7 $149.28   13.271%   $169.0909   $169.09   $169.10   $169.10  
  7 purchase totals = $926.67       $1,016.6929   $1,016.68   $1,016.70   $1,016.80