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 $45.95   9.383%   $50.2615   $50.26   $50.25   $50.30  
  Purchase #2 $211.75   7.628%   $227.9023   $227.90   $227.90   $227.90  
  Purchase #3 $73.85   12.209%   $82.8663   $82.87   $82.85   $82.90  
  Purchase #4 $160.28   7.558%   $172.394   $172.39   $172.40   $172.40  
  Purchase #5 $213.82   10.851%   $237.0216   $237.02   $237.00   $237.00  
  Purchase #6 $188.47   11.779%   $210.6699   $210.67   $210.65   $210.70  
  Purchase #7 $235.64   7.844%   $254.1236   $254.12   $254.10   $254.10  
  7 purchase totals = $1,129.76       $1,235.2392   $1,235.23   $1,235.15   $1,235.30