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 $33.38   5.573%   $35.2403   $35.24   $35.25   $35.20  
  Purchase #2 $17.28   8.378%   $18.7277   $18.73   $18.75   $18.70  
  Purchase #3 $32.60   6.206%   $34.6232   $34.62   $34.60   $34.60  
  Purchase #4 $98.35   8.115%   $106.3311   $106.33   $106.35   $106.30  
  Purchase #5 $220.52   5.126%   $231.8239   $231.82   $231.80   $231.80  
  Purchase #6 $189.32   4.794%   $198.396   $198.40   $198.40   $198.40  
  Purchase #7 $115.42   10.712%   $127.7838   $127.78   $127.80   $127.80  
  7 purchase totals = $706.87       $752.9260   $752.92   $752.95   $752.80