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	$190.29	10.429%	$210.1353	$210.14	$210.15	$210.10
Purchase #2	$138.41	9.554%	$151.6337	$151.63	$151.65	$151.60
Purchase #3	$217.35	12.591%	$244.7165	$244.72	$244.70	$244.70
Purchase #4	$127.63	10.841%	$141.4664	$141.47	$141.45	$141.50
Purchase #5	$224.71	3.205%	$231.912	$231.91	$231.90	$231.90
Purchase #6	$121.97	12.389%	$137.0809	$137.08	$137.10	$137.10
Purchase #7	$55.81	12.119%	$62.5736	$62.57	$62.55	$62.60
7 purchase totals =	$1,076.17		$1,179.5184	$1,179.52	$1,179.50	$1,179.50