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	$215.76	10.846%	$239.1613	$239.16	$239.15	$239.20
Purchase #2	$18.83	4.587%	$19.6937	$19.69	$19.70	$19.70
Purchase #3	$193.94	7.457%	$208.4021	$208.40	$208.40	$208.40
Purchase #4	$40.27	13.570%	$45.7346	$45.73	$45.75	$45.70
Purchase #5	$174.67	12.433%	$196.3867	$196.39	$196.40	$196.40
Purchase #6	$225.33	5.663%	$238.0904	$238.09	$238.10	$238.10
Purchase #7	$36.98	12.482%	$41.5958	$41.60	$41.60	$41.60
7 purchase totals =	$905.78		$989.0646	$989.06	$989.10	$989.10