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	$159.78	13.248%	$180.9477	$180.95	$180.95	$180.90
Purchase #2	$115.34	10.241%	$127.152	$127.15	$127.15	$127.20
Purchase #3	$90.65	11.365%	$100.9524	$100.95	$100.95	$101.00
Purchase #4	$128.30	11.426%	$142.9596	$142.96	$142.95	$143.00
Purchase #5	$181.42	7.216%	$194.5113	$194.51	$194.50	$194.50
Purchase #6	$12.87	5.346%	$13.558	$13.56	$13.55	$13.60
Purchase #7	$35.46	7.311%	$38.0525	$38.05	$38.05	$38.10
7 purchase totals =	$723.82		$798.1335	$798.13	$798.10	$798.30