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	$53.38	10.578%	$59.0265	$59.03	$59.05	$59.00
Purchase #2	$148.27	12.183%	$166.3337	$166.33	$166.35	$166.30
Purchase #3	$202.41	5.335%	$213.2086	$213.21	$213.20	$213.20
Purchase #4	$194.57	10.415%	$214.8345	$214.83	$214.85	$214.80
Purchase #5	$166.60	4.277%	$173.7255	$173.73	$173.75	$173.70
Purchase #6	$12.45	6.637%	$13.2763	$13.28	$13.30	$13.30
Purchase #7	$189.59	5.248%	$199.5397	$199.54	$199.55	$199.50
7 purchase totals =	$967.27		$1,039.9448	$1,039.95	$1,040.05	$1,039.80