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	$223.29	6.768%	$238.4023	$238.40	$238.40	$238.40
Purchase #2	$190.88	13.409%	$216.4751	$216.48	$216.50	$216.50
Purchase #3	$66.46	5.177%	$69.9006	$69.90	$69.90	$69.90
Purchase #4	$166.99	12.381%	$187.665	$187.67	$187.65	$187.70
Purchase #5	$78.78	12.182%	$88.377	$88.38	$88.40	$88.40
Purchase #6	$39.92	10.786%	$44.2258	$44.23	$44.25	$44.20
Purchase #7	$150.69	6.729%	$160.8299	$160.83	$160.85	$160.80
7 purchase totals =	$917.01		$1,005.8757	$1,005.89	$1,005.95	$1,005.90