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 $32.81   3.869%   $34.0794   $34.08   $34.10   $34.10  
  Purchase #2 $169.82   7.612%   $182.7467   $182.75   $182.75   $182.70  
  Purchase #3 $213.98   3.113%   $220.6412   $220.64   $220.65   $220.60  
  Purchase #4 $183.86   9.719%   $201.7294   $201.73   $201.75   $201.70  
  Purchase #5 $179.75   3.252%   $185.5955   $185.60   $185.60   $185.60  
  Purchase #6 $218.66   10.337%   $241.2629   $241.26   $241.25   $241.30  
  Purchase #7 $111.61   7.726%   $120.233   $120.23   $120.25   $120.20  
  7 purchase totals = $1,110.49       $1,186.2881   $1,186.29   $1,186.35   $1,186.20