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	$217.36	6.308%	$231.0711	$231.07	$231.05	$231.10
Purchase #2	$218.56	11.442%	$243.5676	$243.57	$243.55	$243.60
Purchase #3	$120.87	5.410%	$127.4091	$127.41	$127.40	$127.40
Purchase #4	$68.30	5.436%	$72.0128	$72.01	$72.00	$72.00
Purchase #5	$51.32	4.151%	$53.4503	$53.45	$53.45	$53.50
Purchase #6	$172.70	12.821%	$194.8419	$194.84	$194.85	$194.80
Purchase #7	$134.66	6.316%	$143.1651	$143.17	$143.15	$143.20
7 purchase totals =	$983.77		$1,065.5179	$1,065.52	$1,065.45	$1,065.60