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	$141.50	8.708%	$153.8218	$153.82	$153.80	$153.80
Purchase #2	$153.38	5.254%	$161.4386	$161.44	$161.45	$161.40
Purchase #3	$6.71	11.789%	$7.501	$7.50	$7.50	$7.50
Purchase #4	$119.83	9.450%	$131.1539	$131.15	$131.15	$131.20
Purchase #5	$131.35	8.696%	$142.7722	$142.77	$142.75	$142.80
Purchase #6	$246.70	7.382%	$264.9114	$264.91	$264.90	$264.90
Purchase #7	$102.86	13.267%	$116.5064	$116.51	$116.50	$116.50
7 purchase totals =	$902.33		$978.1053	$978.10	$978.05	$978.10