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	$143.95	4.860%	$150.946	$150.95	$150.95	$150.90
Purchase #2	$13.80	3.534%	$14.2877	$14.29	$14.30	$14.30
Purchase #3	$125.84	12.739%	$141.8708	$141.87	$141.85	$141.90
Purchase #4	$53.52	10.819%	$59.3103	$59.31	$59.30	$59.30
Purchase #5	$105.83	9.808%	$116.2098	$116.21	$116.20	$116.20
Purchase #6	$190.45	10.590%	$210.6187	$210.62	$210.60	$210.60
Purchase #7	$183.38	4.535%	$191.6963	$191.70	$191.70	$191.70
7 purchase totals =	$816.77		$884.9396	$884.95	$884.90	$884.90