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	$14.67	12.172%	$16.4556	$16.46	$16.45	$16.50
Purchase #2	$124.69	5.271%	$131.2624	$131.26	$131.25	$131.30
Purchase #3	$51.37	10.731%	$56.8825	$56.88	$56.90	$56.90
Purchase #4	$123.77	6.395%	$131.6851	$131.69	$131.70	$131.70
Purchase #5	$217.50	8.285%	$235.5199	$235.52	$235.50	$235.50
Purchase #6	$90.33	6.861%	$96.5275	$96.53	$96.55	$96.50
Purchase #7	$100.69	13.871%	$114.6567	$114.66	$114.65	$114.70
7 purchase totals =	$723.02		$782.9897	$783.00	$783.00	$783.10