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	$145.64	13.419%	$165.1834	$165.18	$165.20	$165.20
Purchase #2	$127.64	12.524%	$143.6256	$143.63	$143.65	$143.60
Purchase #3	$89.42	3.232%	$92.3101	$92.31	$92.30	$92.30
Purchase #4	$134.76	7.196%	$144.4573	$144.46	$144.45	$144.50
Purchase #5	$187.78	12.210%	$210.7079	$210.71	$210.70	$210.70
Purchase #6	$219.80	12.273%	$246.7761	$246.78	$246.80	$246.80
Purchase #7	$190.41	5.277%	$200.4579	$200.46	$200.45	$200.50
7 purchase totals =	$1,095.45		$1,203.5183	$1,203.53	$1,203.55	$1,203.60