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	$62.30	11.135%	$69.2371	$69.24	$69.25	$69.20
Purchase #2	$158.60	8.332%	$171.8146	$171.81	$171.80	$171.80
Purchase #3	$72.67	7.558%	$78.1624	$78.16	$78.15	$78.20
Purchase #4	$63.30	3.341%	$65.4149	$65.41	$65.40	$65.40
Purchase #5	$37.49	13.289%	$42.472	$42.47	$42.45	$42.50
Purchase #6	$103.55	6.532%	$110.3139	$110.31	$110.30	$110.30
Purchase #7	$82.86	7.195%	$88.8218	$88.82	$88.80	$88.80
7 purchase totals =	$580.77		$626.2367	$626.22	$626.15	$626.20