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	$43.42	7.156%	$46.5271	$46.53	$46.55	$46.50
Purchase #2	$159.61	8.107%	$172.5496	$172.55	$172.55	$172.50
Purchase #3	$35.81	4.770%	$37.5181	$37.52	$37.50	$37.50
Purchase #4	$33.70	3.333%	$34.8232	$34.82	$34.80	$34.80
Purchase #5	$234.28	3.398%	$242.2408	$242.24	$242.25	$242.20
Purchase #6	$73.62	11.703%	$82.2357	$82.24	$82.25	$82.20
Purchase #7	$116.39	10.438%	$128.5388	$128.54	$128.55	$128.50
7 purchase totals =	$696.83		$744.4333	$744.44	$744.45	$744.20