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	$52.85	3.109%	$54.4931	$54.49	$54.50	$54.50
Purchase #2	$22.87	6.865%	$24.44	$24.44	$24.45	$24.40
Purchase #3	$39.42	8.839%	$42.9043	$42.90	$42.90	$42.90
Purchase #4	$151.93	4.244%	$158.3779	$158.38	$158.40	$158.40
Purchase #5	$134.25	7.811%	$144.7363	$144.74	$144.75	$144.70
Purchase #6	$202.92	7.630%	$218.4028	$218.40	$218.40	$218.40
Purchase #7	$225.42	3.483%	$233.2714	$233.27	$233.25	$233.30
7 purchase totals =	$829.66		$876.6258	$876.62	$876.65	$876.60