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	$57.48	5.364%	$60.5632	$60.56	$60.55	$60.60
Purchase #2	$49.76	7.252%	$53.3686	$53.37	$53.35	$53.40
Purchase #3	$205.98	8.116%	$222.6973	$222.70	$222.70	$222.70
Purchase #4	$70.74	10.407%	$78.1019	$78.10	$78.10	$78.10
Purchase #5	$88.96	13.167%	$100.6734	$100.67	$100.65	$100.70
Purchase #6	$44.61	3.625%	$46.2271	$46.23	$46.25	$46.20
Purchase #7	$40.62	13.739%	$46.2008	$46.20	$46.20	$46.20
7 purchase totals =	$558.15		$607.8323	$607.83	$607.80	$607.90