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	$156.61	4.471%	$163.612	$163.61	$163.60	$163.60
Purchase #2	$165.59	10.603%	$183.1475	$183.15	$183.15	$183.10
Purchase #3	$83.89	6.262%	$89.1432	$89.14	$89.15	$89.10
Purchase #4	$114.90	11.757%	$128.4088	$128.41	$128.40	$128.40
Purchase #5	$214.49	9.392%	$234.6349	$234.63	$234.65	$234.60
Purchase #6	$114.77	10.367%	$126.6682	$126.67	$126.65	$126.70
Purchase #7	$117.51	8.872%	$127.9355	$127.94	$127.95	$127.90
7 purchase totals =	$967.76		$1,053.5501	$1,053.55	$1,053.55	$1,053.40