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	$245.56	8.497%	$266.4252	$266.43	$266.45	$266.40
Purchase #2	$25.38	7.865%	$27.3761	$27.38	$27.40	$27.40
Purchase #3	$31.78	6.537%	$33.8575	$33.86	$33.85	$33.90
Purchase #4	$133.31	10.364%	$147.1262	$147.13	$147.15	$147.10
Purchase #5	$29.60	7.743%	$31.8919	$31.89	$31.90	$31.90
Purchase #6	$121.87	11.800%	$136.2507	$136.25	$136.25	$136.30
Purchase #7	$241.66	10.114%	$266.1015	$266.10	$266.10	$266.10
7 purchase totals =	$829.16		$909.0291	$909.04	$909.10	$909.10