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	$35.59	13.814%	$40.5064	$40.51	$40.50	$40.50
Purchase #2	$209.67	4.668%	$219.4574	$219.46	$219.45	$219.50
Purchase #3	$78.66	9.384%	$86.0415	$86.04	$86.05	$86.00
Purchase #4	$226.70	4.517%	$236.94	$236.94	$236.95	$236.90
Purchase #5	$106.58	4.223%	$111.0809	$111.08	$111.10	$111.10
Purchase #6	$156.62	10.813%	$173.5553	$173.56	$173.55	$173.60
Purchase #7	$193.61	3.395%	$200.1831	$200.18	$200.20	$200.20
7 purchase totals =	$1,007.43		$1,067.7646	$1,067.77	$1,067.80	$1,067.80