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	$42.73	3.587%	$44.2627	$44.26	$44.25	$44.30
Purchase #2	$43.31	5.112%	$45.524	$45.52	$45.50	$45.50
Purchase #3	$206.45	4.495%	$215.7299	$215.73	$215.75	$215.70
Purchase #4	$52.83	8.773%	$57.4648	$57.46	$57.45	$57.50
Purchase #5	$37.26	9.252%	$40.7073	$40.71	$40.70	$40.70
Purchase #6	$129.76	5.692%	$137.1459	$137.15	$137.15	$137.10
Purchase #7	$55.69	4.328%	$58.1003	$58.10	$58.10	$58.10
7 purchase totals =	$568.03		$598.9349	$598.93	$598.90	$598.90