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 $212.39   9.623%   $232.8283   $232.83   $232.85   $232.80  
  Purchase #2 $127.99   10.704%   $141.69   $141.69   $141.70   $141.70  
  Purchase #3 $118.40   6.398%   $125.9752   $125.98   $126.00   $126.00  
  Purchase #4 $168.29   4.264%   $175.4659   $175.47   $175.45   $175.50  
  Purchase #5 $64.78   3.158%   $66.8258   $66.83   $66.85   $66.80  
  Purchase #6 $35.39   7.517%   $38.0503   $38.05   $38.05   $38.10  
  Purchase #7 $145.79   3.640%   $151.0968   $151.10   $151.10   $151.10  
  7 purchase totals = $873.03       $931.9323   $931.95   $932.00   $932.00