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	$209.50	10.228%	$230.9277	$230.93	$230.95	$230.90
Purchase #2	$162.77	9.677%	$178.5213	$178.52	$178.50	$178.50
Purchase #3	$30.61	10.521%	$33.8305	$33.83	$33.85	$33.80
Purchase #4	$54.82	8.183%	$59.3059	$59.31	$59.30	$59.30
Purchase #5	$220.88	4.641%	$231.131	$231.13	$231.15	$231.10
Purchase #6	$159.62	6.564%	$170.0975	$170.10	$170.10	$170.10
Purchase #7	$228.64	5.210%	$240.5521	$240.55	$240.55	$240.60
7 purchase totals =	$1,066.84		$1,144.3660	$1,144.37	$1,144.40	$1,144.30