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	$86.80	12.486%	$97.6378	$97.64	$97.65	$97.60
Purchase #2	$86.84	3.465%	$89.849	$89.85	$89.85	$89.80
Purchase #3	$160.61	6.814%	$171.554	$171.55	$171.55	$171.60
Purchase #4	$127.56	3.770%	$132.369	$132.37	$132.35	$132.40
Purchase #5	$71.68	9.184%	$78.2631	$78.26	$78.25	$78.30
Purchase #6	$126.94	6.656%	$135.3891	$135.39	$135.40	$135.40
Purchase #7	$218.42	4.769%	$228.8364	$228.84	$228.85	$228.80
7 purchase totals =	$878.85		$933.8984	$933.90	$933.90	$933.90