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	$205.85	9.170%	$224.7264	$224.73	$224.75	$224.70
Purchase #2	$175.72	9.161%	$191.8177	$191.82	$191.80	$191.80
Purchase #3	$145.45	6.670%	$155.1515	$155.15	$155.15	$155.20
Purchase #4	$180.41	11.298%	$200.7927	$200.79	$200.80	$200.80
Purchase #5	$190.30	8.126%	$205.7638	$205.76	$205.75	$205.80
Purchase #6	$93.92	10.260%	$103.5562	$103.56	$103.55	$103.60
Purchase #7	$194.25	8.754%	$211.2546	$211.25	$211.25	$211.30
7 purchase totals =	$1,185.90		$1,293.0629	$1,293.06	$1,293.05	$1,293.20