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 $230.99   5.284%   $243.1955   $243.20   $243.20   $243.20  
  Purchase #2 $135.53   8.794%   $147.4485   $147.45   $147.45   $147.40  
  Purchase #3 $175.48   4.320%   $183.0607   $183.06   $183.05   $183.10  
  Purchase #4 $154.68   5.479%   $163.1549   $163.15   $163.15   $163.20  
  Purchase #5 $68.58   11.375%   $76.381   $76.38   $76.40   $76.40  
  Purchase #6 $162.46   13.273%   $184.0233   $184.02   $184.00   $184.00  
  Purchase #7 $60.53   3.541%   $62.6734   $62.67   $62.65   $62.70  
  7 purchase totals = $988.25       $1,059.9373   $1,059.93   $1,059.90   $1,060.00