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	$192.87	11.745%	$215.5226	$215.52	$215.50	$215.50
Purchase #2	$153.71	5.676%	$162.4346	$162.43	$162.45	$162.40
Purchase #3	$137.83	4.304%	$143.7622	$143.76	$143.75	$143.80
Purchase #4	$241.69	11.159%	$268.6602	$268.66	$268.65	$268.70
Purchase #5	$119.69	5.705%	$126.5183	$126.52	$126.50	$126.50
Purchase #6	$46.86	12.805%	$52.8604	$52.86	$52.85	$52.90
Purchase #7	$240.73	4.557%	$251.7001	$251.70	$251.70	$251.70
7 purchase totals =	$1,133.38		$1,221.4584	$1,221.45	$1,221.40	$1,221.50