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	$197.55	9.534%	$216.3844	$216.38	$216.40	$216.40
Purchase #2	$156.64	7.124%	$167.799	$167.80	$167.80	$167.80
Purchase #3	$140.92	3.277%	$145.5379	$145.54	$145.55	$145.50
Purchase #4	$192.50	12.114%	$215.8195	$215.82	$215.80	$215.80
Purchase #5	$118.49	8.103%	$128.0912	$128.09	$128.10	$128.10
Purchase #6	$56.99	3.728%	$59.1146	$59.11	$59.10	$59.10
Purchase #7	$151.31	8.674%	$164.4346	$164.43	$164.45	$164.40
7 purchase totals =	$1,014.40		$1,097.1812	$1,097.17	$1,097.20	$1,097.10