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	$85.31	12.363%	$95.8569	$95.86	$95.85	$95.90
Purchase #2	$63.95	10.393%	$70.5963	$70.60	$70.60	$70.60
Purchase #3	$39.51	3.498%	$40.8921	$40.89	$40.90	$40.90
Purchase #4	$187.86	9.246%	$205.2295	$205.23	$205.25	$205.20
Purchase #5	$181.65	9.654%	$199.1865	$199.19	$199.20	$199.20
Purchase #6	$199.39	12.463%	$224.24	$224.24	$224.25	$224.20
Purchase #7	$221.76	9.322%	$242.4325	$242.43	$242.45	$242.40
7 purchase totals =	$979.43		$1,078.4338	$1,078.44	$1,078.50	$1,078.40