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	$222.38	7.107%	$238.1845	$238.18	$238.20	$238.20
Purchase #2	$176.58	11.172%	$196.3075	$196.31	$196.30	$196.30
Purchase #3	$211.25	12.224%	$237.0732	$237.07	$237.05	$237.10
Purchase #4	$244.99	3.241%	$252.9301	$252.93	$252.95	$252.90
Purchase #5	$42.66	6.154%	$45.2853	$45.29	$45.30	$45.30
Purchase #6	$107.76	9.541%	$118.0414	$118.04	$118.05	$118.00
Purchase #7	$119.87	6.606%	$127.7886	$127.79	$127.80	$127.80
7 purchase totals =	$1,125.49		$1,215.6106	$1,215.61	$1,215.65	$1,215.60