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	$179.25	7.716%	$193.0809	$193.08	$193.10	$193.10
Purchase #2	$88.33	10.433%	$97.5455	$97.55	$97.55	$97.50
Purchase #3	$210.78	10.697%	$233.3271	$233.33	$233.35	$233.30
Purchase #4	$72.55	13.146%	$82.0874	$82.09	$82.10	$82.10
Purchase #5	$171.52	11.187%	$190.7079	$190.71	$190.70	$190.70
Purchase #6	$126.72	13.206%	$143.4546	$143.45	$143.45	$143.50
Purchase #7	$190.53	5.514%	$201.0358	$201.04	$201.05	$201.00
7 purchase totals =	$1,039.68		$1,141.2392	$1,141.25	$1,141.30	$1,141.20