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 $88.51   6.524%   $94.2844   $94.28   $94.30   $94.30  
  Purchase #2 $95.42   12.844%   $107.6757   $107.68   $107.70   $107.70  
  Purchase #3 $73.28   11.207%   $81.4925   $81.49   $81.50   $81.50  
  Purchase #4 $79.75   6.394%   $84.8492   $84.85   $84.85   $84.80  
  Purchase #5 $89.35   6.427%   $95.0925   $95.09   $95.10   $95.10  
  Purchase #6 $99.26   13.428%   $112.5886   $112.59   $112.60   $112.60  
  Purchase #7 $139.52   5.402%   $147.0569   $147.06   $147.05   $147.10  
  7 purchase totals = $665.09       $723.0398   $723.04   $723.10   $723.10