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	$166.65	7.194%	$178.6388	$178.64	$178.65	$178.60
Purchase #2	$232.75	9.131%	$254.0024	$254.00	$254.00	$254.00
Purchase #3	$242.34	13.241%	$274.4282	$274.43	$274.45	$274.40
Purchase #4	$56.58	4.585%	$59.1742	$59.17	$59.15	$59.20
Purchase #5	$119.52	3.815%	$124.0797	$124.08	$124.10	$124.10
Purchase #6	$162.31	5.843%	$171.7938	$171.79	$171.80	$171.80
Purchase #7	$34.90	10.635%	$38.6116	$38.61	$38.60	$38.60
7 purchase totals =	$1,015.05		$1,100.7287	$1,100.72	$1,100.75	$1,100.70