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	$134.86	7.275%	$144.6711	$144.67	$144.65	$144.70
Purchase #2	$35.81	6.445%	$38.118	$38.12	$38.10	$38.10
Purchase #3	$100.80	4.862%	$105.7009	$105.70	$105.70	$105.70
Purchase #4	$154.83	8.144%	$167.4394	$167.44	$167.45	$167.40
Purchase #5	$159.28	10.261%	$175.6237	$175.62	$175.60	$175.60
Purchase #6	$185.55	4.754%	$194.371	$194.37	$194.35	$194.40
Purchase #7	$102.79	8.718%	$111.7512	$111.75	$111.75	$111.80
7 purchase totals =	$873.92		$937.6753	$937.67	$937.60	$937.70