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 $216.96   5.253%   $228.3569   $228.36   $228.35   $228.40  
  Purchase #2 $53.99   5.684%   $57.0588   $57.06   $57.05   $57.10  
  Purchase #3 $82.85   8.280%   $89.71   $89.71   $89.70   $89.70  
  Purchase #4 $179.98   10.282%   $198.4855   $198.49   $198.50   $198.50  
  Purchase #5 $250.74   9.352%   $274.1892   $274.19   $274.20   $274.20  
  Purchase #6 $195.58   5.654%   $206.6381   $206.64   $206.65   $206.60  
  Purchase #7 $26.25   9.657%   $28.785   $28.79   $28.80   $28.80  
  7 purchase totals = $1,006.35       $1,083.2235   $1,083.24   $1,083.25   $1,083.30