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	$213.43	9.393%	$233.4775	$233.48	$233.50	$233.50
Purchase #2	$57.48	13.183%	$65.0576	$65.06	$65.05	$65.10
Purchase #3	$244.73	9.476%	$267.9206	$267.92	$267.90	$267.90
Purchase #4	$204.84	11.661%	$228.7264	$228.73	$228.75	$228.70
Purchase #5	$103.83	7.205%	$111.311	$111.31	$111.30	$111.30
Purchase #6	$104.33	13.506%	$118.4208	$118.42	$118.40	$118.40
Purchase #7	$56.34	10.869%	$62.4636	$62.46	$62.45	$62.50
7 purchase totals =	$984.98		$1,087.3775	$1,087.38	$1,087.35	$1,087.40