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	$53.78	13.529%	$61.0559	$61.06	$61.05	$61.10
Purchase #2	$210.49	3.566%	$217.9961	$218.00	$218.00	$218.00
Purchase #3	$189.56	10.301%	$209.0866	$209.09	$209.10	$209.10
Purchase #4	$132.38	3.381%	$136.8558	$136.86	$136.85	$136.90
Purchase #5	$193.88	13.152%	$219.3791	$219.38	$219.40	$219.40
Purchase #6	$224.30	6.280%	$238.386	$238.39	$238.40	$238.40
Purchase #7	$122.71	9.242%	$134.0509	$134.05	$134.05	$134.10
7 purchase totals =	$1,127.10		$1,216.8104	$1,216.83	$1,216.85	$1,217.00