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 $96.46   5.367%   $101.637   $101.64   $101.65   $101.60  
  Purchase #2 $194.46   4.366%   $202.9501   $202.95   $202.95   $203.00  
  Purchase #3 $116.91   8.866%   $127.2752   $127.28   $127.30   $127.30  
  Purchase #4 $42.82   9.797%   $47.0151   $47.02   $47.00   $47.00  
  Purchase #5 $243.43   4.332%   $253.9754   $253.98   $254.00   $254.00  
  Purchase #6 $68.36   5.293%   $71.9783   $71.98   $72.00   $72.00  
  Purchase #7 $133.61   13.179%   $151.2185   $151.22   $151.20   $151.20  
  7 purchase totals = $896.05       $956.0496   $956.07   $956.10   $956.10