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 $211.26   11.471%   $235.4936   $235.49   $235.50   $235.50  
  Purchase #2 $233.53   13.320%   $264.6362   $264.64   $264.65   $264.60  
  Purchase #3 $62.32   13.393%   $70.6665   $70.67   $70.65   $70.70  
  Purchase #4 $156.82   11.859%   $175.4173   $175.42   $175.40   $175.40  
  Purchase #5 $181.71   5.182%   $191.1262   $191.13   $191.15   $191.10  
  Purchase #6 $17.36   11.579%   $19.3701   $19.37   $19.35   $19.40  
  Purchase #7 $165.35   8.764%   $179.8413   $179.84   $179.85   $179.80  
  7 purchase totals = $1,028.35       $1,136.5512   $1,136.56   $1,136.55   $1,136.50