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	$166.77	4.405%	$174.1162	$174.12	$174.10	$174.10
Purchase #2	$194.47	10.825%	$215.5214	$215.52	$215.50	$215.50
Purchase #3	$197.78	7.417%	$212.4493	$212.45	$212.45	$212.40
Purchase #4	$90.34	4.484%	$94.3908	$94.39	$94.40	$94.40
Purchase #5	$92.87	8.532%	$100.7937	$100.79	$100.80	$100.80
Purchase #6	$161.60	3.278%	$166.8972	$166.90	$166.90	$166.90
Purchase #7	$10.74	8.384%	$11.6404	$11.64	$11.65	$11.60
7 purchase totals =	$914.57		$975.8090	$975.81	$975.80	$975.70