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	$208.39	3.340%	$215.3502	$215.35	$215.35	$215.40
Purchase #2	$175.70	5.365%	$185.1263	$185.13	$185.15	$185.10
Purchase #3	$180.96	9.620%	$198.3684	$198.37	$198.35	$198.40
Purchase #4	$160.72	7.784%	$173.2304	$173.23	$173.25	$173.20
Purchase #5	$100.92	9.233%	$110.2379	$110.24	$110.25	$110.20
Purchase #6	$10.56	8.412%	$11.4483	$11.45	$11.45	$11.40
Purchase #7	$206.40	5.283%	$217.3041	$217.30	$217.30	$217.30
7 purchase totals =	$1,043.65		$1,111.0656	$1,111.07	$1,111.10	$1,111.00