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	$199.49	11.551%	$222.5331	$222.53	$222.55	$222.50
Purchase #2	$137.84	9.526%	$150.9706	$150.97	$150.95	$151.00
Purchase #3	$41.91	11.236%	$46.619	$46.62	$46.60	$46.60
Purchase #4	$100.52	8.493%	$109.0572	$109.06	$109.05	$109.10
Purchase #5	$82.60	9.291%	$90.2744	$90.27	$90.25	$90.30
Purchase #6	$31.26	12.617%	$35.2041	$35.20	$35.20	$35.20
Purchase #7	$236.95	13.532%	$269.0141	$269.01	$269.00	$269.00
7 purchase totals =	$830.57		$923.6725	$923.66	$923.60	$923.70