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 $22.83   8.432%   $24.755   $24.76   $24.75   $24.80  
  Purchase #2 $33.84   3.283%   $34.951   $34.95   $34.95   $35.00  
  Purchase #3 $54.86   10.393%   $60.5616   $60.56   $60.55   $60.60  
  Purchase #4 $193.53   12.702%   $218.1122   $218.11   $218.10   $218.10  
  Purchase #5 $64.39   12.815%   $72.6416   $72.64   $72.65   $72.60  
  Purchase #6 $175.94   10.313%   $194.0847   $194.08   $194.10   $194.10  
  Purchase #7 $186.46   5.406%   $196.54   $196.54   $196.55   $196.50  
  7 purchase totals = $731.85       $801.6461   $801.64   $801.65   $801.70