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	$156.56	5.396%	$165.008	$165.01	$165.00	$165.00
Purchase #2	$37.79	3.404%	$39.0764	$39.08	$39.10	$39.10
Purchase #3	$244.91	6.412%	$260.6136	$260.61	$260.60	$260.60
Purchase #4	$230.54	5.107%	$242.3137	$242.31	$242.30	$242.30
Purchase #5	$145.64	11.836%	$162.878	$162.88	$162.90	$162.90
Purchase #6	$49.84	9.653%	$54.6511	$54.65	$54.65	$54.70
Purchase #7	$112.60	4.832%	$118.0408	$118.04	$118.05	$118.00
7 purchase totals =	$977.88		$1,042.5816	$1,042.58	$1,042.60	$1,042.60