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	$231.98	13.670%	$263.6917	$263.69	$263.70	$263.70
Purchase #2	$151.95	13.374%	$172.2718	$172.27	$172.25	$172.30
Purchase #3	$230.52	7.371%	$247.5116	$247.51	$247.50	$247.50
Purchase #4	$105.39	9.604%	$115.5117	$115.51	$115.50	$115.50
Purchase #5	$131.88	8.630%	$143.2612	$143.26	$143.25	$143.30
Purchase #6	$13.49	13.365%	$15.2929	$15.29	$15.30	$15.30
Purchase #7	$59.56	8.478%	$64.6095	$64.61	$64.60	$64.60
7 purchase totals =	$924.77		$1,022.1504	$1,022.14	$1,022.10	$1,022.20