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	$231.49	12.161%	$259.6415	$259.64	$259.65	$259.60
Purchase #2	$188.74	9.730%	$207.1044	$207.10	$207.10	$207.10
Purchase #3	$72.45	8.381%	$78.522	$78.52	$78.50	$78.50
Purchase #4	$207.25	6.340%	$220.3897	$220.39	$220.40	$220.40
Purchase #5	$121.43	10.253%	$133.8802	$133.88	$133.90	$133.90
Purchase #6	$53.34	11.481%	$59.464	$59.46	$59.45	$59.50
Purchase #7	$242.73	3.767%	$251.8736	$251.87	$251.85	$251.90
7 purchase totals =	$1,117.43		$1,210.8754	$1,210.86	$1,210.85	$1,210.90