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 $32.62   10.213%   $35.9515   $35.95   $35.95   $36.00  
  Purchase #2 $194.92   11.323%   $216.9908   $216.99   $217.00   $217.00  
  Purchase #3 $140.64   13.827%   $160.0863   $160.09   $160.10   $160.10  
  Purchase #4 $133.68   7.110%   $143.1846   $143.18   $143.20   $143.20  
  Purchase #5 $177.81   6.571%   $189.4939   $189.49   $189.50   $189.50  
  Purchase #6 $168.82   4.850%   $177.0078   $177.01   $177.00   $177.00  
  Purchase #7 $154.91   3.493%   $160.321   $160.32   $160.30   $160.30  
  7 purchase totals = $1,003.40       $1,083.0359   $1,083.03   $1,083.05   $1,083.10