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 $56.59   7.360%   $60.755   $60.76   $60.75   $60.80  
  Purchase #2 $200.46   4.848%   $210.1783   $210.18   $210.20   $210.20  
  Purchase #3 $182.74   4.261%   $190.5266   $190.53   $190.55   $190.50  
  Purchase #4 $248.51   13.717%   $282.5981   $282.60   $282.60   $282.60  
  Purchase #5 $59.74   7.532%   $64.2396   $64.24   $64.25   $64.20  
  Purchase #6 $228.42   5.305%   $240.5377   $240.54   $240.55   $240.50  
  Purchase #7 $69.76   7.522%   $75.0073   $75.01   $75.00   $75.00  
  7 purchase totals = $1,046.22       $1,123.8426   $1,123.86   $1,123.90   $1,123.80