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 $32.38   10.145%   $35.665   $35.67   $35.65   $35.70  
  Purchase #2 $154.34   7.128%   $165.3414   $165.34   $165.35   $165.30  
  Purchase #3 $241.27   4.196%   $251.3937   $251.39   $251.40   $251.40  
  Purchase #4 $192.70   4.442%   $201.2597   $201.26   $201.25   $201.30  
  Purchase #5 $166.74   6.195%   $177.0695   $177.07   $177.05   $177.10  
  Purchase #6 $106.80   11.113%   $118.6687   $118.67   $118.65   $118.70  
  Purchase #7 $22.91   9.400%   $25.0635   $25.06   $25.05   $25.10  
  7 purchase totals = $917.14       $974.4615   $974.46   $974.40   $974.60