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	$58.53	4.354%	$61.0784	$61.08	$61.10	$61.10
Purchase #2	$80.65	13.558%	$91.5845	$91.58	$91.60	$91.60
Purchase #3	$103.39	7.502%	$111.1463	$111.15	$111.15	$111.10
Purchase #4	$242.70	12.629%	$273.3506	$273.35	$273.35	$273.40
Purchase #5	$32.64	9.843%	$35.8528	$35.85	$35.85	$35.90
Purchase #6	$31.77	12.608%	$35.7756	$35.78	$35.80	$35.80
Purchase #7	$108.97	10.612%	$120.5339	$120.53	$120.55	$120.50
7 purchase totals =	$658.65		$729.3221	$729.32	$729.40	$729.40