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	$127.52	13.291%	$144.4687	$144.47	$144.45	$144.50
Purchase #2	$39.54	4.349%	$41.2596	$41.26	$41.25	$41.30
Purchase #3	$49.58	13.835%	$56.4394	$56.44	$56.45	$56.40
Purchase #4	$27.46	13.407%	$31.1416	$31.14	$31.15	$31.10
Purchase #5	$205.32	4.727%	$215.0255	$215.03	$215.05	$215.00
Purchase #6	$86.58	7.364%	$92.9558	$92.96	$92.95	$93.00
Purchase #7	$233.32	8.475%	$253.0939	$253.09	$253.10	$253.10
7 purchase totals =	$769.32		$834.3845	$834.39	$834.40	$834.40