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	$243.42	9.508%	$266.5644	$266.56	$266.55	$266.60
Purchase #2	$59.59	9.364%	$65.17	$65.17	$65.15	$65.20
Purchase #3	$194.31	10.578%	$214.8641	$214.86	$214.85	$214.90
Purchase #4	$202.52	8.660%	$220.0582	$220.06	$220.05	$220.10
Purchase #5	$63.73	11.231%	$70.8875	$70.89	$70.90	$70.90
Purchase #6	$80.65	3.642%	$83.5873	$83.59	$83.60	$83.60
Purchase #7	$131.61	8.379%	$142.6376	$142.64	$142.65	$142.60
7 purchase totals =	$975.83		$1,063.7691	$1,063.77	$1,063.75	$1,063.90