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	$201.93	10.375%	$222.8802	$222.88	$222.90	$222.90
Purchase #2	$109.84	5.453%	$115.8296	$115.83	$115.85	$115.80
Purchase #3	$35.78	4.845%	$37.5135	$37.51	$37.50	$37.50
Purchase #4	$233.71	3.553%	$242.0137	$242.01	$242.00	$242.00
Purchase #5	$219.72	6.407%	$233.7975	$233.80	$233.80	$233.80
Purchase #6	$20.62	13.221%	$23.3462	$23.35	$23.35	$23.30
Purchase #7	$114.47	12.371%	$128.6311	$128.63	$128.65	$128.60
7 purchase totals =	$936.07		$1,004.0118	$1,004.01	$1,004.05	$1,003.90