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	$209.41	13.413%	$237.4982	$237.50	$237.50	$237.50
Purchase #2	$185.31	4.388%	$193.4414	$193.44	$193.45	$193.40
Purchase #3	$184.89	6.493%	$196.8949	$196.89	$196.90	$196.90
Purchase #4	$174.51	8.762%	$189.8006	$189.80	$189.80	$189.80
Purchase #5	$126.88	10.118%	$139.7177	$139.72	$139.70	$139.70
Purchase #6	$70.94	11.632%	$79.1917	$79.19	$79.20	$79.20
Purchase #7	$166.37	11.504%	$185.5092	$185.51	$185.50	$185.50
7 purchase totals =	$1,118.31		$1,222.0537	$1,222.05	$1,222.05	$1,222.00