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	$207.41	3.590%	$214.856	$214.86	$214.85	$214.90
Purchase #2	$139.76	13.674%	$158.8708	$158.87	$158.85	$158.90
Purchase #3	$156.70	7.743%	$168.8333	$168.83	$168.85	$168.80
Purchase #4	$247.32	13.820%	$281.4996	$281.50	$281.50	$281.50
Purchase #5	$171.50	5.295%	$180.5809	$180.58	$180.60	$180.60
Purchase #6	$49.87	12.127%	$55.9177	$55.92	$55.90	$55.90
Purchase #7	$110.78	4.151%	$115.3785	$115.38	$115.40	$115.40
7 purchase totals =	$1,083.34		$1,175.9368	$1,175.94	$1,175.95	$1,176.00