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	$153.69	8.395%	$166.5923	$166.59	$166.60	$166.60
Purchase #2	$119.96	11.755%	$134.0613	$134.06	$134.05	$134.10
Purchase #3	$153.82	3.300%	$158.8961	$158.90	$158.90	$158.90
Purchase #4	$58.74	12.297%	$65.9633	$65.96	$65.95	$66.00
Purchase #5	$160.70	7.510%	$172.7686	$172.77	$172.75	$172.80
Purchase #6	$191.86	4.657%	$200.7949	$200.79	$200.80	$200.80
Purchase #7	$5.98	4.719%	$6.2622	$6.26	$6.25	$6.30
7 purchase totals =	$844.75		$905.3387	$905.33	$905.30	$905.50