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 $182.69   6.678%   $194.89   $194.89   $194.90   $194.90  
  Purchase #2 $216.52   9.285%   $236.6239   $236.62   $236.60   $236.60  
  Purchase #3 $195.44   8.349%   $211.7573   $211.76   $211.75   $211.80  
  Purchase #4 $226.44   5.541%   $238.987   $238.99   $239.00   $239.00  
  Purchase #5 $149.61   12.300%   $168.012   $168.01   $168.00   $168.00  
  Purchase #6 $236.51   6.246%   $251.2824   $251.28   $251.30   $251.30  
  Purchase #7 $177.48   11.507%   $197.9026   $197.90   $197.90   $197.90  
  7 purchase totals = $1,384.69       $1,499.4552   $1,499.45   $1,499.45   $1,499.50