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	$197.42	9.387%	$215.9518	$215.95	$215.95	$216.00
Purchase #2	$59.88	3.116%	$61.7459	$61.75	$61.75	$61.70
Purchase #3	$37.30	12.749%	$42.0554	$42.06	$42.05	$42.10
Purchase #4	$161.39	10.697%	$178.6539	$178.65	$178.65	$178.70
Purchase #5	$217.29	5.773%	$229.8342	$229.83	$229.85	$229.80
Purchase #6	$98.42	9.372%	$107.6439	$107.64	$107.65	$107.60
Purchase #7	$159.77	5.133%	$167.971	$167.97	$167.95	$168.00
7 purchase totals =	$931.47		$1,003.8561	$1,003.85	$1,003.85	$1,003.90