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 $211.61   11.509%   $235.9642   $235.96   $235.95   $236.00  
  Purchase #2 $84.57   11.348%   $94.167   $94.17   $94.15   $94.20  
  Purchase #3 $34.47   13.213%   $39.0245   $39.02   $39.00   $39.00  
  Purchase #4 $89.55   7.654%   $96.4042   $96.40   $96.40   $96.40  
  Purchase #5 $195.52   7.761%   $210.6943   $210.69   $210.70   $210.70  
  Purchase #6 $210.97   7.744%   $227.3075   $227.31   $227.30   $227.30  
  Purchase #7 $182.53   10.650%   $201.9694   $201.97   $201.95   $202.00  
  7 purchase totals = $1,009.22       $1,105.5311   $1,105.52   $1,105.45   $1,105.60