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	$98.89	10.850%	$109.6196	$109.62	$109.60	$109.60
Purchase #2	$178.93	9.634%	$196.1681	$196.17	$196.15	$196.20
Purchase #3	$176.50	7.283%	$189.3545	$189.35	$189.35	$189.40
Purchase #4	$233.96	8.509%	$253.8677	$253.87	$253.85	$253.90
Purchase #5	$35.36	3.404%	$36.5637	$36.56	$36.55	$36.60
Purchase #6	$184.90	5.665%	$195.3746	$195.37	$195.35	$195.40
Purchase #7	$23.98	3.421%	$24.8004	$24.80	$24.80	$24.80
7 purchase totals =	$932.52		$1,005.7486	$1,005.74	$1,005.65	$1,005.90