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	$160.41	3.345%	$165.7757	$165.78	$165.80	$165.80
Purchase #2	$102.88	4.123%	$107.1217	$107.12	$107.10	$107.10
Purchase #3	$126.70	3.273%	$130.8469	$130.85	$130.85	$130.80
Purchase #4	$161.72	11.666%	$180.5863	$180.59	$180.60	$180.60
Purchase #5	$30.36	6.186%	$32.2381	$32.24	$32.25	$32.20
Purchase #6	$159.35	7.348%	$171.059	$171.06	$171.05	$171.10
Purchase #7	$240.72	5.706%	$254.4555	$254.46	$254.45	$254.50
7 purchase totals =	$982.14		$1,042.0832	$1,042.10	$1,042.10	$1,042.10