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	$164.40	8.549%	$178.4546	$178.45	$178.45	$178.50
Purchase #2	$232.87	10.820%	$258.0665	$258.07	$258.05	$258.10
Purchase #3	$158.49	10.522%	$175.1663	$175.17	$175.15	$175.20
Purchase #4	$56.51	4.465%	$59.0332	$59.03	$59.05	$59.00
Purchase #5	$180.88	3.787%	$187.7299	$187.73	$187.75	$187.70
Purchase #6	$72.87	8.190%	$78.8381	$78.84	$78.85	$78.80
Purchase #7	$152.70	4.583%	$159.6982	$159.70	$159.70	$159.70
7 purchase totals =	$1,018.72		$1,096.9868	$1,096.99	$1,097.00	$1,097.00