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	$152.52	10.623%	$168.7222	$168.72	$168.70	$168.70
Purchase #2	$118.36	6.565%	$126.1303	$126.13	$126.15	$126.10
Purchase #3	$65.27	10.341%	$72.0196	$72.02	$72.00	$72.00
Purchase #4	$222.31	7.396%	$238.752	$238.75	$238.75	$238.80
Purchase #5	$64.50	5.533%	$68.0688	$68.07	$68.05	$68.10
Purchase #6	$132.56	5.747%	$140.1782	$140.18	$140.20	$140.20
Purchase #7	$88.79	3.155%	$91.5913	$91.59	$91.60	$91.60
7 purchase totals =	$844.31		$905.4624	$905.46	$905.45	$905.50