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	$148.53	4.661%	$155.453	$155.45	$155.45	$155.50
Purchase #2	$21.27	4.186%	$22.1604	$22.16	$22.15	$22.20
Purchase #3	$57.31	8.545%	$62.2071	$62.21	$62.20	$62.20
Purchase #4	$115.68	6.612%	$123.3288	$123.33	$123.35	$123.30
Purchase #5	$204.29	5.630%	$215.7915	$215.79	$215.80	$215.80
Purchase #6	$136.53	11.572%	$152.3293	$152.33	$152.35	$152.30
Purchase #7	$139.71	13.290%	$158.2775	$158.28	$158.30	$158.30
7 purchase totals =	$823.32		$889.5476	$889.55	$889.60	$889.60