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 $243.94   7.521%   $262.2867   $262.29   $262.30   $262.30  
  Purchase #2 $201.74   11.169%   $224.2723   $224.27   $224.25   $224.30  
  Purchase #3 $109.85   12.491%   $123.5714   $123.57   $123.55   $123.60  
  Purchase #4 $155.98   8.467%   $169.1868   $169.19   $169.20   $169.20  
  Purchase #5 $228.88   8.718%   $248.8338   $248.83   $248.85   $248.80  
  Purchase #6 $142.61   7.249%   $152.9478   $152.95   $152.95   $152.90  
  Purchase #7 $151.32   9.198%   $165.2384   $165.24   $165.25   $165.20  
  7 purchase totals = $1,234.32       $1,346.3372   $1,346.34   $1,346.35   $1,346.30