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	$176.82	5.815%	$187.1021	$187.10	$187.10	$187.10
Purchase #2	$133.53	6.370%	$142.0359	$142.04	$142.05	$142.00
Purchase #3	$130.91	6.292%	$139.1469	$139.15	$139.15	$139.10
Purchase #4	$34.40	13.850%	$39.1644	$39.16	$39.15	$39.20
Purchase #5	$80.86	10.427%	$89.2913	$89.29	$89.30	$89.30
Purchase #6	$65.73	13.492%	$74.5983	$74.60	$74.60	$74.60
Purchase #7	$32.98	4.195%	$34.3635	$34.36	$34.35	$34.40
7 purchase totals =	$655.23		$705.7024	$705.70	$705.70	$705.70