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 $182.47   11.230%   $202.9614   $202.96   $202.95   $203.00  
  Purchase #2 $186.89   4.449%   $195.2047   $195.20   $195.20   $195.20  
  Purchase #3 $198.49   11.864%   $222.0389   $222.04   $222.05   $222.00  
  Purchase #4 $92.43   8.164%   $99.976   $99.98   $100.00   $100.00  
  Purchase #5 $88.29   9.852%   $96.9883   $96.99   $97.00   $97.00  
  Purchase #6 $224.32   4.369%   $234.1205   $234.12   $234.10   $234.10  
  Purchase #7 $43.99   10.270%   $48.5078   $48.51   $48.50   $48.50  
  7 purchase totals = $1,016.88       $1,099.7976   $1,099.80   $1,099.80   $1,099.80