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 $213.68   5.832%   $226.1418   $226.14   $226.15   $226.10  
  Purchase #2 $94.47   4.359%   $98.5879   $98.59   $98.60   $98.60  
  Purchase #3 $169.56   6.740%   $180.9883   $180.99   $181.00   $181.00  
  Purchase #4 $185.77   8.320%   $201.2261   $201.23   $201.25   $201.20  
  Purchase #5 $104.29   6.817%   $111.3994   $111.40   $111.40   $111.40  
  Purchase #6 $115.91   7.640%   $124.7655   $124.77   $124.75   $124.80  
  Purchase #7 $115.29   12.734%   $129.971   $129.97   $129.95   $130.00  
  7 purchase totals = $998.97       $1,073.0800   $1,073.09   $1,073.10   $1,073.10