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	$144.76	5.160%	$152.2296	$152.23	$152.25	$152.20
Purchase #2	$11.54	10.234%	$12.721	$12.72	$12.70	$12.70
Purchase #3	$181.26	10.258%	$199.8537	$199.85	$199.85	$199.90
Purchase #4	$184.86	3.322%	$191.001	$191.00	$191.00	$191.00
Purchase #5	$173.56	8.636%	$188.5486	$188.55	$188.55	$188.50
Purchase #6	$123.60	11.355%	$137.6348	$137.63	$137.65	$137.60
Purchase #7	$46.44	10.829%	$51.469	$51.47	$51.45	$51.50
7 purchase totals =	$866.02		$933.4577	$933.45	$933.45	$933.40