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	$193.25	8.243%	$209.1796	$209.18	$209.20	$209.20
Purchase #2	$39.54	8.269%	$42.8096	$42.81	$42.80	$42.80
Purchase #3	$163.87	13.759%	$186.4169	$186.42	$186.40	$186.40
Purchase #4	$36.77	12.577%	$41.3946	$41.39	$41.40	$41.40
Purchase #5	$107.41	3.403%	$111.0652	$111.07	$111.05	$111.10
Purchase #6	$224.72	11.209%	$249.9089	$249.91	$249.90	$249.90
Purchase #7	$240.30	11.367%	$267.6149	$267.61	$267.60	$267.60
7 purchase totals =	$1,005.86		$1,108.3897	$1,108.39	$1,108.35	$1,108.40