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	$162.79	13.589%	$184.9115	$184.91	$184.90	$184.90
Purchase #2	$101.98	5.515%	$107.6042	$107.60	$107.60	$107.60
Purchase #3	$166.70	11.290%	$185.5204	$185.52	$185.50	$185.50
Purchase #4	$126.90	7.592%	$136.5342	$136.53	$136.55	$136.50
Purchase #5	$78.80	13.776%	$89.6555	$89.66	$89.65	$89.70
Purchase #6	$164.93	10.634%	$182.4687	$182.47	$182.45	$182.50
Purchase #7	$131.50	13.147%	$148.7883	$148.79	$148.80	$148.80
7 purchase totals =	$933.60		$1,035.4828	$1,035.48	$1,035.45	$1,035.50