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 $182.27   6.662%   $194.4128   $194.41   $194.40   $194.40  
  Purchase #2 $50.96   5.167%   $53.5931   $53.59   $53.60   $53.60  
  Purchase #3 $172.63   8.210%   $186.8029   $186.80   $186.80   $186.80  
  Purchase #4 $48.45   8.385%   $52.5125   $52.51   $52.50   $52.50  
  Purchase #5 $94.36   8.259%   $102.1532   $102.15   $102.15   $102.20  
  Purchase #6 $44.40   4.559%   $46.4242   $46.42   $46.40   $46.40  
  Purchase #7 $112.69   7.689%   $121.3547   $121.35   $121.35   $121.40  
  7 purchase totals = $705.76       $757.2534   $757.23   $757.20   $757.30