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	$181.75	9.210%	$198.4892	$198.49	$198.50	$198.50
Purchase #2	$62.66	4.831%	$65.6871	$65.69	$65.70	$65.70
Purchase #3	$27.69	3.847%	$28.7552	$28.76	$28.75	$28.80
Purchase #4	$23.57	8.380%	$25.5452	$25.55	$25.55	$25.50
Purchase #5	$146.53	8.255%	$158.6261	$158.63	$158.65	$158.60
Purchase #6	$99.69	5.786%	$105.4581	$105.46	$105.45	$105.50
Purchase #7	$190.53	10.517%	$210.568	$210.57	$210.55	$210.60
7 purchase totals =	$732.42		$793.1289	$793.15	$793.15	$793.20