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 $46.38   13.562%   $52.6701   $52.67   $52.65   $52.70  
  Purchase #2 $245.39   11.596%   $273.8454   $273.85   $273.85   $273.80  
  Purchase #3 $26.49   13.285%   $30.0092   $30.01   $30.00   $30.00  
  Purchase #4 $85.98   12.540%   $96.7619   $96.76   $96.75   $96.80  
  Purchase #5 $215.55   13.120%   $243.8302   $243.83   $243.85   $243.80  
  Purchase #6 $75.27   5.433%   $79.3594   $79.36   $79.35   $79.40  
  Purchase #7 $162.61   10.106%   $179.0434   $179.04   $179.05   $179.00  
  7 purchase totals = $857.67       $955.5196   $955.52   $955.50   $955.50