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 $200.59   5.222%   $211.0648   $211.06   $211.05   $211.10  
  Purchase #2 $173.68   9.563%   $190.289   $190.29   $190.30   $190.30  
  Purchase #3 $24.70   6.437%   $26.2899   $26.29   $26.30   $26.30  
  Purchase #4 $118.32   4.496%   $123.6397   $123.64   $123.65   $123.60  
  Purchase #5 $178.26   13.864%   $202.974   $202.97   $202.95   $203.00  
  Purchase #6 $197.76   13.264%   $223.9909   $223.99   $224.00   $224.00  
  Purchase #7 $168.81   7.394%   $181.2918   $181.29   $181.30   $181.30  
  7 purchase totals = $1,062.12       $1,159.5401   $1,159.53   $1,159.55   $1,159.60