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	$142.93	8.667%	$155.3177	$155.32	$155.30	$155.30
Purchase #2	$102.72	8.441%	$111.3906	$111.39	$111.40	$111.40
Purchase #3	$148.88	4.446%	$155.4992	$155.50	$155.50	$155.50
Purchase #4	$215.74	8.110%	$233.2365	$233.24	$233.25	$233.20
Purchase #5	$210.97	9.280%	$230.548	$230.55	$230.55	$230.50
Purchase #6	$194.46	9.443%	$212.8229	$212.82	$212.80	$212.80
Purchase #7	$103.53	8.522%	$112.3528	$112.35	$112.35	$112.40
7 purchase totals =	$1,119.23		$1,211.1677	$1,211.17	$1,211.15	$1,211.10