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	$101.41	12.377%	$113.9615	$113.96	$113.95	$114.00
Purchase #2	$138.96	9.590%	$152.2863	$152.29	$152.30	$152.30
Purchase #3	$115.44	3.235%	$119.1745	$119.17	$119.15	$119.20
Purchase #4	$177.92	8.384%	$192.8368	$192.84	$192.85	$192.80
Purchase #5	$85.29	5.268%	$89.7831	$89.78	$89.80	$89.80
Purchase #6	$144.48	7.206%	$154.8912	$154.89	$154.90	$154.90
Purchase #7	$242.42	8.845%	$263.862	$263.86	$263.85	$263.90
7 purchase totals =	$1,005.92		$1,086.7954	$1,086.79	$1,086.80	$1,086.90