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	$79.30	13.325%	$89.8667	$89.87	$89.85	$89.90
Purchase #2	$87.64	8.200%	$94.8265	$94.83	$94.85	$94.80
Purchase #3	$189.47	10.550%	$209.4591	$209.46	$209.45	$209.50
Purchase #4	$218.54	5.540%	$230.6471	$230.65	$230.65	$230.60
Purchase #5	$227.92	12.124%	$255.553	$255.55	$255.55	$255.60
Purchase #6	$6.62	3.195%	$6.8315	$6.83	$6.85	$6.80
Purchase #7	$172.81	4.464%	$180.5242	$180.52	$180.50	$180.50
7 purchase totals =	$982.30		$1,067.7081	$1,067.71	$1,067.70	$1,067.70