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	$198.39	5.439%	$209.1804	$209.18	$209.20	$209.20
Purchase #2	$191.30	12.752%	$215.6946	$215.69	$215.70	$215.70
Purchase #3	$211.85	8.695%	$230.2704	$230.27	$230.25	$230.30
Purchase #4	$47.32	7.799%	$51.0105	$51.01	$51.00	$51.00
Purchase #5	$54.57	3.527%	$56.4947	$56.49	$56.50	$56.50
Purchase #6	$89.66	13.610%	$101.8627	$101.86	$101.85	$101.90
Purchase #7	$35.83	4.539%	$37.4563	$37.46	$37.45	$37.50
7 purchase totals =	$828.92		$901.9696	$901.96	$901.95	$902.10