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	$190.85	9.440%	$208.8662	$208.87	$208.85	$208.90
Purchase #2	$88.83	13.348%	$100.687	$100.69	$100.70	$100.70
Purchase #3	$237.72	12.467%	$267.3566	$267.36	$267.35	$267.40
Purchase #4	$219.42	9.738%	$240.7871	$240.79	$240.80	$240.80
Purchase #5	$20.38	6.463%	$21.6972	$21.70	$21.70	$21.70
Purchase #6	$176.63	11.310%	$196.6069	$196.61	$196.60	$196.60
Purchase #7	$49.79	7.185%	$53.3674	$53.37	$53.35	$53.40
7 purchase totals =	$983.62		$1,089.3684	$1,089.39	$1,089.35	$1,089.50