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	$96.31	13.336%	$109.1539	$109.15	$109.15	$109.20
Purchase #2	$204.47	4.117%	$212.888	$212.89	$212.90	$212.90
Purchase #3	$67.82	6.412%	$72.1686	$72.17	$72.15	$72.20
Purchase #4	$103.57	8.548%	$112.4232	$112.42	$112.40	$112.40
Purchase #5	$49.40	6.326%	$52.525	$52.53	$52.55	$52.50
Purchase #6	$28.41	5.263%	$29.9052	$29.91	$29.90	$29.90
Purchase #7	$157.31	12.523%	$177.0099	$177.01	$177.00	$177.00
7 purchase totals =	$707.29		$766.0738	$766.08	$766.05	$766.10