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 $230.94   5.482%   $243.6001   $243.60   $243.60   $243.60  
  Purchase #2 $158.57   8.185%   $171.549   $171.55   $171.55   $171.50  
  Purchase #3 $77.83   10.313%   $85.8566   $85.86   $85.85   $85.90  
  Purchase #4 $174.52   5.805%   $184.6509   $184.65   $184.65   $184.70  
  Purchase #5 $213.43   3.366%   $220.6141   $220.61   $220.60   $220.60  
  Purchase #6 $175.64   11.156%   $195.2344   $195.23   $195.25   $195.20  
  Purchase #7 $43.68   13.807%   $49.7109   $49.71   $49.70   $49.70  
  7 purchase totals = $1,074.61       $1,151.2160   $1,151.21   $1,151.20   $1,151.20