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	$148.39	3.451%	$153.5109	$153.51	$153.50	$153.50
Purchase #2	$169.31	8.194%	$183.1833	$183.18	$183.20	$183.20
Purchase #3	$33.29	7.584%	$35.8147	$35.81	$35.80	$35.80
Purchase #4	$123.54	3.568%	$127.9479	$127.95	$127.95	$127.90
Purchase #5	$166.38	10.476%	$183.81	$183.81	$183.80	$183.80
Purchase #6	$125.67	4.271%	$131.0374	$131.04	$131.05	$131.00
Purchase #7	$209.98	8.852%	$228.5674	$228.57	$228.55	$228.60
7 purchase totals =	$976.56		$1,043.8716	$1,043.87	$1,043.85	$1,043.80