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 $192.34   5.328%   $202.5879   $202.59   $202.60   $202.60  
  Purchase #2 $153.72   3.449%   $159.0218   $159.02   $159.00   $159.00  
  Purchase #3 $207.69   10.479%   $229.4538   $229.45   $229.45   $229.50  
  Purchase #4 $57.89   3.342%   $59.8247   $59.82   $59.80   $59.80  
  Purchase #5 $146.65   5.870%   $155.2584   $155.26   $155.25   $155.30  
  Purchase #6 $164.80   5.605%   $174.037   $174.04   $174.05   $174.00  
  Purchase #7 $241.86   10.798%   $267.976   $267.98   $268.00   $268.00  
  7 purchase totals = $1,164.95       $1,248.1596   $1,248.16   $1,248.15   $1,248.20