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	$34.88	9.602%	$38.2292	$38.23	$38.25	$38.20
Purchase #2	$74.76	4.386%	$78.039	$78.04	$78.05	$78.00
Purchase #3	$99.54	5.811%	$105.3243	$105.32	$105.30	$105.30
Purchase #4	$201.94	4.759%	$211.5503	$211.55	$211.55	$211.60
Purchase #5	$94.69	13.866%	$107.8197	$107.82	$107.80	$107.80
Purchase #6	$226.61	4.286%	$236.3225	$236.32	$236.30	$236.30
Purchase #7	$229.80	4.321%	$239.7297	$239.73	$239.75	$239.70
7 purchase totals =	$962.22		$1,017.0147	$1,017.01	$1,017.00	$1,016.90