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	$200.76	12.654%	$226.1642	$226.16	$226.15	$226.20
Purchase #2	$124.68	13.311%	$141.2762	$141.28	$141.30	$141.30
Purchase #3	$94.62	12.639%	$106.579	$106.58	$106.60	$106.60
Purchase #4	$207.76	9.571%	$227.6447	$227.64	$227.65	$227.60
Purchase #5	$158.45	4.494%	$165.5707	$165.57	$165.55	$165.60
Purchase #6	$106.50	6.610%	$113.5397	$113.54	$113.55	$113.50
Purchase #7	$31.94	11.800%	$35.7089	$35.71	$35.70	$35.70
7 purchase totals =	$924.71		$1,016.4834	$1,016.48	$1,016.50	$1,016.50