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	$26.37	6.471%	$28.0764	$28.08	$28.10	$28.10
Purchase #2	$64.83	8.385%	$70.266	$70.27	$70.25	$70.30
Purchase #3	$75.86	8.453%	$82.2724	$82.27	$82.25	$82.30
Purchase #4	$112.41	5.666%	$118.7792	$118.78	$118.80	$118.80
Purchase #5	$113.47	3.347%	$117.2678	$117.27	$117.25	$117.30
Purchase #6	$103.28	12.823%	$116.5236	$116.52	$116.50	$116.50
Purchase #7	$222.78	4.654%	$233.1482	$233.15	$233.15	$233.10
7 purchase totals =	$719.00		$766.3336	$766.34	$766.30	$766.40