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 $54.84   12.201%   $61.531   $61.53   $61.55   $61.50  
  Purchase #2 $124.76   4.236%   $130.0448   $130.04   $130.05   $130.00  
  Purchase #3 $112.81   10.214%   $124.3324   $124.33   $124.35   $124.30  
  Purchase #4 $46.64   13.380%   $52.8804   $52.88   $52.90   $52.90  
  Purchase #5 $24.49   6.691%   $26.1286   $26.13   $26.15   $26.10  
  Purchase #6 $12.68   9.344%   $13.8648   $13.86   $13.85   $13.90  
  Purchase #7 $55.31   4.479%   $57.7873   $57.79   $57.80   $57.80  
  7 purchase totals = $431.53       $466.5693   $466.56   $466.65   $466.50