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	$240.68	7.303%	$258.2569	$258.26	$258.25	$258.30
Purchase #2	$43.55	4.518%	$45.5176	$45.52	$45.50	$45.50
Purchase #3	$85.35	10.563%	$94.3655	$94.37	$94.35	$94.40
Purchase #4	$202.60	5.523%	$213.7896	$213.79	$213.80	$213.80
Purchase #5	$19.85	6.569%	$21.1539	$21.15	$21.15	$21.20
Purchase #6	$123.85	7.851%	$133.5735	$133.57	$133.55	$133.60
Purchase #7	$242.83	3.298%	$250.8385	$250.84	$250.85	$250.80
7 purchase totals =	$958.71		$1,017.4955	$1,017.50	$1,017.45	$1,017.60