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	$52.86	4.842%	$55.4195	$55.42	$55.40	$55.40
Purchase #2	$179.78	4.296%	$187.5033	$187.50	$187.50	$187.50
Purchase #3	$222.96	13.796%	$253.7196	$253.72	$253.70	$253.70
Purchase #4	$161.26	3.559%	$166.9992	$167.00	$167.00	$167.00
Purchase #5	$245.30	3.849%	$254.7416	$254.74	$254.75	$254.70
Purchase #6	$149.46	3.798%	$155.1365	$155.14	$155.15	$155.10
Purchase #7	$205.81	10.317%	$227.0434	$227.04	$227.05	$227.00
7 purchase totals =	$1,217.43		$1,300.5631	$1,300.56	$1,300.55	$1,300.40