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	$144.72	9.717%	$158.7824	$158.78	$158.80	$158.80
Purchase #2	$115.81	10.191%	$127.6122	$127.61	$127.60	$127.60
Purchase #3	$243.31	5.440%	$256.5461	$256.55	$256.55	$256.50
Purchase #4	$211.35	12.208%	$237.1516	$237.15	$237.15	$237.20
Purchase #5	$9.30	6.214%	$9.8779	$9.88	$9.90	$9.90
Purchase #6	$242.89	6.789%	$259.3798	$259.38	$259.40	$259.40
Purchase #7	$147.42	6.190%	$156.5453	$156.55	$156.55	$156.50
7 purchase totals =	$1,114.80		$1,205.8953	$1,205.90	$1,205.95	$1,205.90