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	$202.65	10.340%	$223.604	$223.60	$223.60	$223.60
Purchase #2	$215.76	3.516%	$223.3461	$223.35	$223.35	$223.30
Purchase #3	$230.28	4.448%	$240.5229	$240.52	$240.50	$240.50
Purchase #4	$192.94	5.139%	$202.8552	$202.86	$202.85	$202.90
Purchase #5	$69.93	11.543%	$78.002	$78.00	$78.00	$78.00
Purchase #6	$150.37	6.401%	$159.9952	$160.00	$160.00	$160.00
Purchase #7	$19.83	12.579%	$22.3244	$22.32	$22.30	$22.30
7 purchase totals =	$1,081.76		$1,150.6498	$1,150.65	$1,150.60	$1,150.60