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	$68.67	12.231%	$77.069	$77.07	$77.05	$77.10
Purchase #2	$18.46	3.183%	$19.0476	$19.05	$19.05	$19.00
Purchase #3	$233.72	13.326%	$264.8655	$264.87	$264.85	$264.90
Purchase #4	$221.75	6.400%	$235.942	$235.94	$235.95	$235.90
Purchase #5	$151.74	8.373%	$164.4452	$164.45	$164.45	$164.40
Purchase #6	$215.43	10.707%	$238.4961	$238.50	$238.50	$238.50
Purchase #7	$242.84	3.321%	$250.9047	$250.90	$250.90	$250.90
7 purchase totals =	$1,152.61		$1,250.7701	$1,250.78	$1,250.75	$1,250.70