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	$215.85	8.238%	$233.6317	$233.63	$233.65	$233.60
Purchase #2	$38.49	9.417%	$42.1146	$42.11	$42.10	$42.10
Purchase #3	$51.87	7.635%	$55.8303	$55.83	$55.85	$55.80
Purchase #4	$210.88	3.522%	$218.3072	$218.31	$218.30	$218.30
Purchase #5	$247.56	3.174%	$255.4176	$255.42	$255.40	$255.40
Purchase #6	$200.92	10.458%	$221.9322	$221.93	$221.95	$221.90
Purchase #7	$250.56	6.373%	$266.5282	$266.53	$266.55	$266.50
7 purchase totals =	$1,216.13		$1,293.7618	$1,293.76	$1,293.80	$1,293.60