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	$14.88	5.518%	$15.7011	$15.70	$15.70	$15.70
Purchase #2	$219.58	10.229%	$242.0408	$242.04	$242.05	$242.00
Purchase #3	$246.31	3.779%	$255.6181	$255.62	$255.60	$255.60
Purchase #4	$196.37	10.723%	$217.4268	$217.43	$217.45	$217.40
Purchase #5	$169.35	10.718%	$187.5009	$187.50	$187.50	$187.50
Purchase #6	$169.61	4.281%	$176.871	$176.87	$176.85	$176.90
Purchase #7	$26.89	4.587%	$28.1234	$28.12	$28.10	$28.10
7 purchase totals =	$1,042.99		$1,123.2821	$1,123.28	$1,123.25	$1,123.20