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 $71.92   5.647%   $75.9813   $75.98   $76.00   $76.00  
  Purchase #2 $199.53   5.807%   $211.1167   $211.12   $211.10   $211.10  
  Purchase #3 $28.60   13.672%   $32.5102   $32.51   $32.50   $32.50  
  Purchase #4 $94.66   5.399%   $99.7707   $99.77   $99.75   $99.80  
  Purchase #5 $207.45   11.671%   $231.6615   $231.66   $231.65   $231.70  
  Purchase #6 $130.67   4.871%   $137.0349   $137.03   $137.05   $137.00  
  Purchase #7 $192.75   11.571%   $215.0531   $215.05   $215.05   $215.10  
  7 purchase totals = $925.58       $1,003.1284   $1,003.12   $1,003.10   $1,003.20