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	$130.35	12.210%	$146.2657	$146.27	$146.25	$146.30
Purchase #2	$129.46	7.768%	$139.5165	$139.52	$139.50	$139.50
Purchase #3	$200.88	11.346%	$223.6718	$223.67	$223.65	$223.70
Purchase #4	$20.68	9.382%	$22.6202	$22.62	$22.60	$22.60
Purchase #5	$126.77	10.845%	$140.5182	$140.52	$140.50	$140.50
Purchase #6	$34.43	12.636%	$38.7806	$38.78	$38.80	$38.80
Purchase #7	$218.90	6.757%	$233.6911	$233.69	$233.70	$233.70
7 purchase totals =	$861.47		$945.0641	$945.07	$945.00	$945.10