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	$175.56	11.856%	$196.3744	$196.37	$196.35	$196.40
Purchase #2	$59.56	9.137%	$65.002	$65.00	$65.00	$65.00
Purchase #3	$81.47	12.401%	$91.5731	$91.57	$91.55	$91.60
Purchase #4	$122.84	11.364%	$136.7995	$136.80	$136.80	$136.80
Purchase #5	$17.88	7.129%	$19.1547	$19.15	$19.15	$19.20
Purchase #6	$124.49	10.445%	$137.493	$137.49	$137.50	$137.50
Purchase #7	$98.55	12.130%	$110.5041	$110.50	$110.50	$110.50
7 purchase totals =	$680.35		$756.9008	$756.88	$756.85	$757.00