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 $58.59   5.832%   $62.007   $62.01   $62.00   $62.00  
  Purchase #2 $175.60   13.490%   $199.2884   $199.29   $199.30   $199.30  
  Purchase #3 $15.91   12.270%   $17.8622   $17.86   $17.85   $17.90  
  Purchase #4 $207.52   13.632%   $235.8091   $235.81   $235.80   $235.80  
  Purchase #5 $52.92   3.668%   $54.8611   $54.86   $54.85   $54.90  
  Purchase #6 $206.66   7.217%   $221.5747   $221.57   $221.55   $221.60  
  Purchase #7 $21.64   11.286%   $24.0823   $24.08   $24.10   $24.10  
  7 purchase totals = $738.84       $815.4848   $815.48   $815.45   $815.60