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	$53.86	10.852%	$59.7049	$59.70	$59.70	$59.70
Purchase #2	$30.97	5.259%	$32.5987	$32.60	$32.60	$32.60
Purchase #3	$217.82	3.694%	$225.8663	$225.87	$225.85	$225.90
Purchase #4	$134.74	6.538%	$143.5493	$143.55	$143.55	$143.50
Purchase #5	$217.74	6.847%	$232.6487	$232.65	$232.65	$232.60
Purchase #6	$86.83	5.775%	$91.8444	$91.84	$91.85	$91.80
Purchase #7	$103.76	10.219%	$114.3632	$114.36	$114.35	$114.40
7 purchase totals =	$845.72		$900.5755	$900.57	$900.55	$900.50