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 $62.92   5.515%   $66.39   $66.39   $66.40   $66.40  
  Purchase #2 $238.88   11.283%   $265.8328   $265.83   $265.85   $265.80  
  Purchase #3 $179.33   12.806%   $202.295   $202.30   $202.30   $202.30  
  Purchase #4 $250.99   10.259%   $276.7391   $276.74   $276.75   $276.70  
  Purchase #5 $187.32   5.210%   $197.0794   $197.08   $197.10   $197.10  
  Purchase #6 $50.35   8.169%   $54.4631   $54.46   $54.45   $54.50  
  Purchase #7 $44.86   8.660%   $48.7449   $48.74   $48.75   $48.70  
  7 purchase totals = $1,014.65       $1,111.5443   $1,111.54   $1,111.60   $1,111.50