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	$179.72	10.594%	$198.7595	$198.76	$198.75	$198.80
Purchase #2	$246.30	13.456%	$279.4421	$279.44	$279.45	$279.40
Purchase #3	$66.60	8.719%	$72.4069	$72.41	$72.40	$72.40
Purchase #4	$153.86	3.287%	$158.9174	$158.92	$158.90	$158.90
Purchase #5	$69.43	11.225%	$77.2235	$77.22	$77.20	$77.20
Purchase #6	$78.84	7.753%	$84.9525	$84.95	$84.95	$85.00
Purchase #7	$222.69	7.508%	$239.4096	$239.41	$239.40	$239.40
7 purchase totals =	$1,017.44		$1,111.1115	$1,111.11	$1,111.05	$1,111.10