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	$80.90	10.333%	$89.2594	$89.26	$89.25	$89.30
Purchase #2	$167.30	3.299%	$172.8192	$172.82	$172.80	$172.80
Purchase #3	$43.46	10.112%	$47.8547	$47.85	$47.85	$47.90
Purchase #4	$11.93	4.186%	$12.4294	$12.43	$12.45	$12.40
Purchase #5	$193.29	10.752%	$214.0725	$214.07	$214.05	$214.10
Purchase #6	$85.37	4.764%	$89.437	$89.44	$89.45	$89.40
Purchase #7	$97.31	13.599%	$110.5432	$110.54	$110.55	$110.50
7 purchase totals =	$679.56		$736.4154	$736.41	$736.40	$736.40