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	$40.63	8.693%	$44.162	$44.16	$44.15	$44.20
Purchase #2	$220.37	13.139%	$249.3244	$249.32	$249.30	$249.30
Purchase #3	$80.45	6.852%	$85.9624	$85.96	$85.95	$86.00
Purchase #4	$54.50	13.867%	$62.0575	$62.06	$62.05	$62.10
Purchase #5	$196.76	5.802%	$208.176	$208.18	$208.20	$208.20
Purchase #6	$154.98	3.412%	$160.2679	$160.27	$160.25	$160.30
Purchase #7	$215.68	10.780%	$238.9303	$238.93	$238.95	$238.90
7 purchase totals =	$963.37		$1,048.8805	$1,048.88	$1,048.85	$1,049.00