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	$12.78	13.719%	$14.5333	$14.53	$14.55	$14.50
Purchase #2	$39.27	9.616%	$43.0462	$43.05	$43.05	$43.00
Purchase #3	$198.76	13.506%	$225.6045	$225.60	$225.60	$225.60
Purchase #4	$59.49	5.718%	$62.8916	$62.89	$62.90	$62.90
Purchase #5	$172.41	13.141%	$195.0664	$195.07	$195.05	$195.10
Purchase #6	$85.69	10.745%	$94.8974	$94.90	$94.90	$94.90
Purchase #7	$93.82	4.758%	$98.284	$98.28	$98.30	$98.30
7 purchase totals =	$662.22		$734.3234	$734.32	$734.35	$734.30