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	$239.70	5.323%	$252.4592	$252.46	$252.45	$252.50
Purchase #2	$120.77	6.621%	$128.7662	$128.77	$128.75	$128.80
Purchase #3	$174.57	12.553%	$196.4838	$196.48	$196.50	$196.50
Purchase #4	$127.29	6.131%	$135.0941	$135.09	$135.10	$135.10
Purchase #5	$124.55	10.259%	$137.3276	$137.33	$137.35	$137.30
Purchase #6	$138.53	3.166%	$142.9159	$142.92	$142.90	$142.90
Purchase #7	$12.89	7.192%	$13.817	$13.82	$13.80	$13.80
7 purchase totals =	$938.30		$1,006.8638	$1,006.87	$1,006.85	$1,006.90