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	$219.76	6.181%	$233.3434	$233.34	$233.35	$233.30
Purchase #2	$198.51	9.192%	$216.757	$216.76	$216.75	$216.80
Purchase #3	$53.99	3.845%	$56.0659	$56.07	$56.05	$56.10
Purchase #4	$40.45	11.616%	$45.1487	$45.15	$45.15	$45.10
Purchase #5	$227.97	4.455%	$238.1261	$238.13	$238.15	$238.10
Purchase #6	$57.52	11.515%	$64.1434	$64.14	$64.15	$64.10
Purchase #7	$250.48	6.304%	$266.2703	$266.27	$266.25	$266.30
7 purchase totals =	$1,048.68		$1,119.8548	$1,119.86	$1,119.85	$1,119.80