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	$239.28	10.523%	$264.4594	$264.46	$264.45	$264.50
Purchase #2	$132.64	6.501%	$141.2629	$141.26	$141.25	$141.30
Purchase #3	$48.60	6.132%	$51.5802	$51.58	$51.60	$51.60
Purchase #4	$163.72	9.288%	$178.9263	$178.93	$178.95	$178.90
Purchase #5	$200.46	10.855%	$222.2199	$222.22	$222.20	$222.20
Purchase #6	$79.69	13.615%	$90.5398	$90.54	$90.55	$90.50
Purchase #7	$169.89	13.651%	$193.0817	$193.08	$193.10	$193.10
7 purchase totals =	$1,034.28		$1,142.0702	$1,142.07	$1,142.10	$1,142.10