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	$25.64	9.412%	$28.0532	$28.05	$28.05	$28.10
Purchase #2	$90.81	5.782%	$96.0606	$96.06	$96.05	$96.10
Purchase #3	$139.95	8.205%	$151.4329	$151.43	$151.45	$151.40
Purchase #4	$151.25	10.757%	$167.52	$167.52	$167.50	$167.50
Purchase #5	$56.33	11.413%	$62.7589	$62.76	$62.75	$62.80
Purchase #6	$8.63	3.398%	$8.9232	$8.92	$8.90	$8.90
Purchase #7	$211.77	10.333%	$233.6522	$233.65	$233.65	$233.70
7 purchase totals =	$684.38		$748.4010	$748.39	$748.35	$748.50