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	$156.58	9.437%	$171.3565	$171.36	$171.35	$171.40
Purchase #2	$141.98	11.804%	$158.7393	$158.74	$158.75	$158.70
Purchase #3	$30.25	10.746%	$33.5007	$33.50	$33.50	$33.50
Purchase #4	$22.83	4.214%	$23.7921	$23.79	$23.80	$23.80
Purchase #5	$28.68	13.194%	$32.464	$32.46	$32.45	$32.50
Purchase #6	$191.78	4.361%	$200.1435	$200.14	$200.15	$200.10
Purchase #7	$231.83	11.476%	$258.4348	$258.43	$258.45	$258.40
7 purchase totals =	$803.93		$878.4309	$878.42	$878.45	$878.40