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	$128.83	6.170%	$136.7788	$136.78	$136.80	$136.80
Purchase #2	$55.88	6.607%	$59.572	$59.57	$59.55	$59.60
Purchase #3	$99.26	6.395%	$105.6077	$105.61	$105.60	$105.60
Purchase #4	$109.63	6.417%	$116.665	$116.67	$116.65	$116.70
Purchase #5	$111.38	6.859%	$119.0196	$119.02	$119.00	$119.00
Purchase #6	$16.92	10.648%	$18.7216	$18.72	$18.70	$18.70
Purchase #7	$147.58	10.381%	$162.9003	$162.90	$162.90	$162.90
7 purchase totals =	$669.48		$719.2650	$719.27	$719.20	$719.30