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	$83.27	12.380%	$93.5788	$93.58	$93.60	$93.60
Purchase #2	$230.57	13.103%	$260.7816	$260.78	$260.80	$260.80
Purchase #3	$181.83	5.487%	$191.807	$191.81	$191.80	$191.80
Purchase #4	$71.77	6.755%	$76.6181	$76.62	$76.60	$76.60
Purchase #5	$112.94	12.582%	$127.1501	$127.15	$127.15	$127.20
Purchase #6	$155.32	13.408%	$176.1453	$176.15	$176.15	$176.10
Purchase #7	$38.51	12.308%	$43.2498	$43.25	$43.25	$43.20
7 purchase totals =	$874.21		$969.3307	$969.34	$969.35	$969.30