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	$12.94	4.205%	$13.4841	$13.48	$13.50	$13.50
Purchase #2	$107.64	9.279%	$117.6279	$117.63	$117.65	$117.60
Purchase #3	$52.37	13.600%	$59.4923	$59.49	$59.50	$59.50
Purchase #4	$102.32	8.615%	$111.1349	$111.13	$111.15	$111.10
Purchase #5	$182.52	10.753%	$202.1464	$202.15	$202.15	$202.10
Purchase #6	$9.99	3.576%	$10.3472	$10.35	$10.35	$10.30
Purchase #7	$178.63	7.414%	$191.8736	$191.87	$191.85	$191.90
7 purchase totals =	$646.41		$706.1064	$706.10	$706.15	$706.00