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	$166.83	10.205%	$183.855	$183.86	$183.85	$183.90
Purchase #2	$176.35	4.228%	$183.8061	$183.81	$183.80	$183.80
Purchase #3	$99.25	5.121%	$104.3326	$104.33	$104.35	$104.30
Purchase #4	$56.37	11.553%	$62.8824	$62.88	$62.90	$62.90
Purchase #5	$106.85	5.628%	$112.8635	$112.86	$112.85	$112.90
Purchase #6	$99.48	8.104%	$107.5419	$107.54	$107.55	$107.50
Purchase #7	$9.92	9.621%	$10.8744	$10.87	$10.85	$10.90
7 purchase totals =	$715.05		$766.1559	$766.15	$766.15	$766.20