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	$244.81	13.272%	$277.3012	$277.30	$277.30	$277.30
Purchase #2	$73.91	5.535%	$78.0009	$78.00	$78.00	$78.00
Purchase #3	$154.53	9.110%	$168.6077	$168.61	$168.60	$168.60
Purchase #4	$154.82	11.536%	$172.68	$172.68	$172.70	$172.70
Purchase #5	$105.42	11.668%	$117.7204	$117.72	$117.70	$117.70
Purchase #6	$186.57	5.610%	$197.0366	$197.04	$197.05	$197.00
Purchase #7	$5.39	4.384%	$5.6263	$5.63	$5.65	$5.60
7 purchase totals =	$925.45		$1,016.9731	$1,016.98	$1,017.00	$1,016.90