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	$215.73	6.697%	$230.1774	$230.18	$230.20	$230.20
Purchase #2	$41.37	4.201%	$43.108	$43.11	$43.10	$43.10
Purchase #3	$205.41	4.247%	$214.1338	$214.13	$214.15	$214.10
Purchase #4	$93.70	10.235%	$103.2902	$103.29	$103.30	$103.30
Purchase #5	$212.61	7.104%	$227.7138	$227.71	$227.70	$227.70
Purchase #6	$28.46	10.262%	$31.3806	$31.38	$31.40	$31.40
Purchase #7	$160.26	3.781%	$166.3194	$166.32	$166.30	$166.30
7 purchase totals =	$957.54		$1,016.1232	$1,016.12	$1,016.15	$1,016.10