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 $63.86   11.157%   $70.9849   $70.98   $71.00   $71.00  
  Purchase #2 $96.71   8.594%   $105.0213   $105.02   $105.00   $105.00  
  Purchase #3 $220.67   7.153%   $236.4545   $236.45   $236.45   $236.50  
  Purchase #4 $226.39   11.416%   $252.2347   $252.23   $252.25   $252.20  
  Purchase #5 $83.59   13.790%   $95.1171   $95.12   $95.10   $95.10  
  Purchase #6 $200.71   3.223%   $207.1789   $207.18   $207.20   $207.20  
  Purchase #7 $97.54   13.348%   $110.5596   $110.56   $110.55   $110.60  
  7 purchase totals = $989.47       $1,077.5510   $1,077.54   $1,077.55   $1,077.60