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 $70.34   8.137%   $76.0636   $76.06   $76.05   $76.10  
  Purchase #2 $168.84   6.204%   $179.3148   $179.31   $179.30   $179.30  
  Purchase #3 $237.43   13.191%   $268.7494   $268.75   $268.75   $268.70  
  Purchase #4 $94.42   11.726%   $105.4917   $105.49   $105.50   $105.50  
  Purchase #5 $150.67   6.288%   $160.1441   $160.14   $160.15   $160.10  
  Purchase #6 $250.65   5.164%   $263.5936   $263.59   $263.60   $263.60  
  Purchase #7 $43.49   5.167%   $45.7371   $45.74   $45.75   $45.70  
  7 purchase totals = $1,015.84       $1,099.0943   $1,099.08   $1,099.10   $1,099.00