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 $62.97   9.164%   $68.7406   $68.74   $68.75   $68.70  
  Purchase #2 $239.45   11.832%   $267.7817   $267.78   $267.80   $267.80  
  Purchase #3 $236.99   9.108%   $258.575   $258.58   $258.60   $258.60  
  Purchase #4 $50.64   4.342%   $52.8388   $52.84   $52.85   $52.80  
  Purchase #5 $186.42   11.383%   $207.6402   $207.64   $207.65   $207.60  
  Purchase #6 $88.70   7.825%   $95.6408   $95.64   $95.65   $95.60  
  Purchase #7 $54.52   8.632%   $59.2262   $59.23   $59.25   $59.20  
  7 purchase totals = $919.69       $1,010.4433   $1,010.45   $1,010.55   $1,010.30