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	$152.40	5.675%	$161.0487	$161.05	$161.05	$161.00
Purchase #2	$208.67	6.343%	$221.9059	$221.91	$221.90	$221.90
Purchase #3	$30.59	13.134%	$34.6077	$34.61	$34.60	$34.60
Purchase #4	$68.51	4.610%	$71.6683	$71.67	$71.65	$71.70
Purchase #5	$112.65	12.850%	$127.1255	$127.13	$127.15	$127.10
Purchase #6	$43.30	7.290%	$46.4566	$46.46	$46.45	$46.50
Purchase #7	$100.69	11.179%	$111.9461	$111.95	$111.95	$111.90
7 purchase totals =	$716.81		$774.7588	$774.78	$774.75	$774.70