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 $35.68   6.532%   $38.0106   $38.01   $38.00   $38.00  
  Purchase #2 $233.65   6.359%   $248.5078   $248.51   $248.50   $248.50  
  Purchase #3 $194.39   5.267%   $204.6285   $204.63   $204.65   $204.60  
  Purchase #4 $74.65   9.336%   $81.6193   $81.62   $81.60   $81.60  
  Purchase #5 $164.70   12.258%   $184.8889   $184.89   $184.90   $184.90  
  Purchase #6 $189.39   7.570%   $203.7268   $203.73   $203.75   $203.70  
  Purchase #7 $227.50   3.110%   $234.5753   $234.58   $234.60   $234.60  
  7 purchase totals = $1,119.96       $1,195.9572   $1,195.97   $1,196.00   $1,195.90