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	$149.35	13.142%	$168.9776	$168.98	$169.00	$169.00
Purchase #2	$232.66	9.826%	$255.5212	$255.52	$255.50	$255.50
Purchase #3	$172.76	7.438%	$185.6099	$185.61	$185.60	$185.60
Purchase #4	$59.60	6.532%	$63.4931	$63.49	$63.50	$63.50
Purchase #5	$73.47	4.671%	$76.9018	$76.90	$76.90	$76.90
Purchase #6	$232.69	4.194%	$242.449	$242.45	$242.45	$242.40
Purchase #7	$68.42	6.164%	$72.6374	$72.64	$72.65	$72.60
7 purchase totals =	$988.95		$1,065.5900	$1,065.59	$1,065.60	$1,065.50