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	$235.94	4.351%	$246.2057	$246.21	$246.20	$246.20
Purchase #2	$105.50	4.202%	$109.9331	$109.93	$109.95	$109.90
Purchase #3	$5.46	13.690%	$6.2075	$6.21	$6.20	$6.20
Purchase #4	$231.48	8.382%	$250.8827	$250.88	$250.90	$250.90
Purchase #5	$200.60	10.823%	$222.3109	$222.31	$222.30	$222.30
Purchase #6	$62.28	5.307%	$65.5852	$65.59	$65.60	$65.60
Purchase #7	$110.97	3.171%	$114.4889	$114.49	$114.50	$114.50
7 purchase totals =	$952.23		$1,015.6140	$1,015.62	$1,015.65	$1,015.60