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	$76.25	10.741%	$84.44	$84.44	$84.45	$84.40
Purchase #2	$111.66	10.846%	$123.7706	$123.77	$123.75	$123.80
Purchase #3	$68.66	4.325%	$71.6295	$71.63	$71.65	$71.60
Purchase #4	$39.32	7.299%	$42.19	$42.19	$42.20	$42.20
Purchase #5	$10.25	8.470%	$11.1182	$11.12	$11.10	$11.10
Purchase #6	$180.94	10.463%	$199.8718	$199.87	$199.85	$199.90
Purchase #7	$134.64	5.164%	$141.5928	$141.59	$141.60	$141.60
7 purchase totals =	$621.72		$674.6129	$674.61	$674.60	$674.60