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	$68.35	12.332%	$76.7789	$76.78	$76.80	$76.80
Purchase #2	$65.30	10.265%	$72.003	$72.00	$72.00	$72.00
Purchase #3	$83.84	9.745%	$92.0102	$92.01	$92.00	$92.00
Purchase #4	$162.35	5.156%	$170.7208	$170.72	$170.70	$170.70
Purchase #5	$228.33	4.422%	$238.4268	$238.43	$238.45	$238.40
Purchase #6	$206.63	9.454%	$226.1648	$226.16	$226.15	$226.20
Purchase #7	$183.30	7.145%	$196.3968	$196.40	$196.40	$196.40
7 purchase totals =	$998.10		$1,072.5013	$1,072.50	$1,072.50	$1,072.50