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	$62.98	11.320%	$70.1093	$70.11	$70.10	$70.10
Purchase #2	$21.83	4.279%	$22.7641	$22.76	$22.75	$22.80
Purchase #3	$38.76	7.741%	$41.7604	$41.76	$41.75	$41.80
Purchase #4	$52.42	3.746%	$54.3837	$54.38	$54.40	$54.40
Purchase #5	$172.38	11.434%	$192.0899	$192.09	$192.10	$192.10
Purchase #6	$94.26	6.551%	$100.435	$100.44	$100.45	$100.40
Purchase #7	$107.93	9.591%	$118.2816	$118.28	$118.30	$118.30
7 purchase totals =	$550.56		$599.8240	$599.82	$599.85	$599.90