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	$155.44	3.415%	$160.7483	$160.75	$160.75	$160.70
Purchase #2	$44.80	5.559%	$47.2904	$47.29	$47.30	$47.30
Purchase #3	$38.39	13.493%	$43.57	$43.57	$43.55	$43.60
Purchase #4	$200.83	11.286%	$223.4957	$223.50	$223.50	$223.50
Purchase #5	$108.50	5.244%	$114.1897	$114.19	$114.20	$114.20
Purchase #6	$243.99	4.695%	$255.4453	$255.45	$255.45	$255.40
Purchase #7	$132.45	13.674%	$150.5612	$150.56	$150.55	$150.60
7 purchase totals =	$924.40		$995.3006	$995.31	$995.30	$995.30