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	$54.91	10.578%	$60.7184	$60.72	$60.70	$60.70
Purchase #2	$146.47	13.666%	$166.4866	$166.49	$166.50	$166.50
Purchase #3	$218.77	10.825%	$242.4519	$242.45	$242.45	$242.50
Purchase #4	$79.96	6.668%	$85.2917	$85.29	$85.30	$85.30
Purchase #5	$183.51	9.319%	$200.6113	$200.61	$200.60	$200.60
Purchase #6	$166.85	5.802%	$176.5306	$176.53	$176.55	$176.50
Purchase #7	$49.64	3.232%	$51.2444	$51.24	$51.25	$51.20
7 purchase totals =	$900.11		$983.3349	$983.33	$983.35	$983.30