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	$129.30	8.348%	$140.094	$140.09	$140.10	$140.10
Purchase #2	$203.95	10.611%	$225.5911	$225.59	$225.60	$225.60
Purchase #3	$200.95	5.766%	$212.5368	$212.54	$212.55	$212.50
Purchase #4	$249.29	6.105%	$264.5092	$264.51	$264.50	$264.50
Purchase #5	$57.87	3.501%	$59.896	$59.90	$59.90	$59.90
Purchase #6	$119.46	13.758%	$135.8953	$135.90	$135.90	$135.90
Purchase #7	$59.46	10.323%	$65.5981	$65.60	$65.60	$65.60
7 purchase totals =	$1,020.28		$1,104.1205	$1,104.13	$1,104.15	$1,104.10