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 $175.39   11.807%   $196.0983   $196.10   $196.10   $196.10  
  Purchase #2 $66.93   10.857%   $74.1966   $74.20   $74.20   $74.20  
  Purchase #3 $157.30   13.150%   $177.985   $177.99   $178.00   $178.00  
  Purchase #4 $126.83   13.402%   $143.8278   $143.83   $143.85   $143.80  
  Purchase #5 $70.56   4.200%   $73.5235   $73.52   $73.50   $73.50  
  Purchase #6 $73.61   3.222%   $75.9817   $75.98   $76.00   $76.00  
  Purchase #7 $241.76   13.852%   $275.2486   $275.25   $275.25   $275.20  
  7 purchase totals = $912.38       $1,016.8615   $1,016.87   $1,016.90   $1,016.80