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	$201.72	10.129%	$222.1522	$222.15	$222.15	$222.20
Purchase #2	$124.96	13.216%	$141.4747	$141.47	$141.45	$141.50
Purchase #3	$204.69	5.835%	$216.6337	$216.63	$216.65	$216.60
Purchase #4	$53.69	7.705%	$57.8268	$57.83	$57.85	$57.80
Purchase #5	$174.30	7.771%	$187.8449	$187.84	$187.85	$187.80
Purchase #6	$176.90	13.291%	$200.4118	$200.41	$200.40	$200.40
Purchase #7	$67.87	3.413%	$70.1864	$70.19	$70.20	$70.20
7 purchase totals =	$1,004.13		$1,096.5305	$1,096.52	$1,096.55	$1,096.50