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	$198.85	10.307%	$219.3455	$219.35	$219.35	$219.30
Purchase #2	$227.96	9.484%	$249.5797	$249.58	$249.60	$249.60
Purchase #3	$135.81	6.692%	$144.8984	$144.90	$144.90	$144.90
Purchase #4	$21.42	13.150%	$24.2367	$24.24	$24.25	$24.20
Purchase #5	$142.36	11.412%	$158.6061	$158.61	$158.60	$158.60
Purchase #6	$156.80	9.288%	$171.3636	$171.36	$171.35	$171.40
Purchase #7	$43.87	12.757%	$49.4665	$49.47	$49.45	$49.50
7 purchase totals =	$927.07		$1,017.4965	$1,017.51	$1,017.50	$1,017.50