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	$215.79	8.152%	$233.3812	$233.38	$233.40	$233.40
Purchase #2	$143.32	13.224%	$162.2726	$162.27	$162.25	$162.30
Purchase #3	$50.25	3.252%	$51.8841	$51.88	$51.90	$51.90
Purchase #4	$50.48	4.748%	$52.8768	$52.88	$52.90	$52.90
Purchase #5	$157.70	6.209%	$167.4916	$167.49	$167.50	$167.50
Purchase #6	$135.65	12.548%	$152.6714	$152.67	$152.65	$152.70
Purchase #7	$226.75	13.298%	$256.9032	$256.90	$256.90	$256.90
7 purchase totals =	$979.94		$1,077.4809	$1,077.47	$1,077.50	$1,077.60