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	$213.62	5.716%	$225.8305	$225.83	$225.85	$225.80
Purchase #2	$129.50	11.123%	$143.9043	$143.90	$143.90	$143.90
Purchase #3	$120.26	6.139%	$127.6428	$127.64	$127.65	$127.60
Purchase #4	$26.87	4.112%	$27.9749	$27.97	$27.95	$28.00
Purchase #5	$25.65	6.602%	$27.3434	$27.34	$27.35	$27.30
Purchase #6	$206.81	12.226%	$232.0946	$232.09	$232.10	$232.10
Purchase #7	$89.80	11.839%	$100.4314	$100.43	$100.45	$100.40
7 purchase totals =	$812.51		$885.2219	$885.20	$885.25	$885.10