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	$130.42	5.642%	$137.7783	$137.78	$137.80	$137.80
Purchase #2	$89.88	3.757%	$93.2568	$93.26	$93.25	$93.30
Purchase #3	$62.91	4.201%	$65.5528	$65.55	$65.55	$65.60
Purchase #4	$247.67	9.666%	$271.6098	$271.61	$271.60	$271.60
Purchase #5	$186.60	7.325%	$200.2685	$200.27	$200.25	$200.30
Purchase #6	$226.46	6.262%	$240.6409	$240.64	$240.65	$240.60
Purchase #7	$185.83	7.230%	$199.2655	$199.27	$199.25	$199.30
7 purchase totals =	$1,129.77		$1,208.3726	$1,208.38	$1,208.35	$1,208.50