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	$215.76	8.172%	$233.3919	$233.39	$233.40	$233.40
Purchase #2	$48.63	4.565%	$50.85	$50.85	$50.85	$50.90
Purchase #3	$102.65	10.796%	$113.7321	$113.73	$113.75	$113.70
Purchase #4	$100.76	5.731%	$106.5346	$106.53	$106.55	$106.50
Purchase #5	$43.83	5.565%	$46.2691	$46.27	$46.25	$46.30
Purchase #6	$138.83	11.694%	$155.0648	$155.06	$155.05	$155.10
Purchase #7	$110.86	11.666%	$123.7929	$123.79	$123.80	$123.80
7 purchase totals =	$761.32		$829.6354	$829.62	$829.65	$829.70