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 $173.95   7.840%   $187.5877   $187.59   $187.60   $187.60  
  Purchase #2 $129.57   7.805%   $139.6829   $139.68   $139.70   $139.70  
  Purchase #3 $135.86   5.414%   $143.2155   $143.22   $143.20   $143.20  
  Purchase #4 $248.36   8.627%   $269.786   $269.79   $269.80   $269.80  
  Purchase #5 $210.74   12.421%   $236.916   $236.92   $236.90   $236.90  
  Purchase #6 $101.66   11.325%   $113.173   $113.17   $113.15   $113.20  
  Purchase #7 $108.54   6.781%   $115.9001   $115.90   $115.90   $115.90  
  7 purchase totals = $1,108.68       $1,206.2612   $1,206.27   $1,206.25   $1,206.30