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	$101.47	10.323%	$111.9447	$111.94	$111.95	$111.90
Purchase #2	$144.39	4.749%	$151.2471	$151.25	$151.25	$151.20
Purchase #3	$146.64	9.802%	$161.0137	$161.01	$161.00	$161.00
Purchase #4	$204.84	9.274%	$223.8369	$223.84	$223.85	$223.80
Purchase #5	$19.31	4.816%	$20.24	$20.24	$20.25	$20.20
Purchase #6	$41.99	8.225%	$45.4437	$45.44	$45.45	$45.40
Purchase #7	$56.34	10.597%	$62.3103	$62.31	$62.30	$62.30
7 purchase totals =	$714.98		$776.0364	$776.03	$776.05	$775.80