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	$9.84	10.234%	$10.847	$10.85	$10.85	$10.80
Purchase #2	$73.45	6.818%	$78.4578	$78.46	$78.45	$78.50
Purchase #3	$204.31	12.648%	$230.1511	$230.15	$230.15	$230.20
Purchase #4	$159.94	4.780%	$167.5851	$167.59	$167.60	$167.60
Purchase #5	$105.83	12.135%	$118.6725	$118.67	$118.65	$118.70
Purchase #6	$96.93	10.402%	$107.0127	$107.01	$107.00	$107.00
Purchase #7	$219.34	8.874%	$238.8042	$238.80	$238.80	$238.80
7 purchase totals =	$869.64		$951.5304	$951.53	$951.50	$951.60