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 $211.76   10.631%   $234.2722   $234.27   $234.25   $234.30  
  Purchase #2 $65.52   8.359%   $70.9968   $71.00   $71.00   $71.00  
  Purchase #3 $93.33   10.860%   $103.4656   $103.47   $103.45   $103.50  
  Purchase #4 $241.94   10.144%   $266.4824   $266.48   $266.50   $266.50  
  Purchase #5 $216.45   13.648%   $245.9911   $245.99   $246.00   $246.00  
  Purchase #6 $49.29   6.810%   $52.6466   $52.65   $52.65   $52.60  
  Purchase #7 $236.26   6.657%   $251.9878   $251.99   $252.00   $252.00  
  7 purchase totals = $1,114.55       $1,225.8425   $1,225.85   $1,225.85   $1,225.90