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	$229.38	8.423%	$248.7007	$248.70	$248.70	$248.70
Purchase #2	$165.93	12.156%	$186.1005	$186.10	$186.10	$186.10
Purchase #3	$190.31	13.437%	$215.882	$215.88	$215.90	$215.90
Purchase #4	$117.67	12.837%	$132.7753	$132.78	$132.80	$132.80
Purchase #5	$122.35	7.362%	$131.3574	$131.36	$131.35	$131.40
Purchase #6	$86.68	3.672%	$89.8629	$89.86	$89.85	$89.90
Purchase #7	$62.92	12.240%	$70.6214	$70.62	$70.60	$70.60
7 purchase totals =	$975.24		$1,075.3002	$1,075.30	$1,075.30	$1,075.40