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	$142.74	13.230%	$161.6245	$161.62	$161.60	$161.60
Purchase #2	$98.35	13.565%	$111.6912	$111.69	$111.70	$111.70
Purchase #3	$17.61	7.532%	$18.9364	$18.94	$18.95	$18.90
Purchase #4	$169.50	12.102%	$190.0129	$190.01	$190.00	$190.00
Purchase #5	$187.85	4.767%	$196.8048	$196.80	$196.80	$196.80
Purchase #6	$83.80	8.796%	$91.171	$91.17	$91.15	$91.20
Purchase #7	$231.40	3.422%	$239.3185	$239.32	$239.30	$239.30
7 purchase totals =	$931.25		$1,009.5593	$1,009.55	$1,009.50	$1,009.50