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	$183.59	4.765%	$192.3381	$192.34	$192.35	$192.30
Purchase #2	$40.67	5.608%	$42.9508	$42.95	$42.95	$43.00
Purchase #3	$228.53	9.848%	$251.0356	$251.04	$251.05	$251.00
Purchase #4	$118.71	7.341%	$127.4245	$127.42	$127.40	$127.40
Purchase #5	$18.76	4.539%	$19.6115	$19.61	$19.60	$19.60
Purchase #6	$171.63	10.710%	$190.0116	$190.01	$190.00	$190.00
Purchase #7	$98.56	11.826%	$110.2157	$110.22	$110.20	$110.20
7 purchase totals =	$860.45		$933.5878	$933.59	$933.55	$933.50