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 $232.96   3.702%   $241.5842   $241.58   $241.60   $241.60  
  Purchase #2 $129.93   3.377%   $134.3177   $134.32   $134.30   $134.30  
  Purchase #3 $25.25   3.623%   $26.1648   $26.16   $26.15   $26.20  
  Purchase #4 $244.93   13.576%   $278.1817   $278.18   $278.20   $278.20  
  Purchase #5 $58.77   3.441%   $60.7923   $60.79   $60.80   $60.80  
  Purchase #6 $179.30   3.207%   $185.0502   $185.05   $185.05   $185.10  
  Purchase #7 $203.35   9.684%   $223.0424   $223.04   $223.05   $223.00  
  7 purchase totals = $1,074.49       $1,149.1333   $1,149.12   $1,149.15   $1,149.20